I'm scared of the universe

I know that the Buddha didn't answer metaphysical questions since it made no sense to him.

No, no, no. This is a catastrophic misperception. Nagarjuna explains why the Buddha steered clear of metaphysical questions. It was because they made complete sense to him. But the answers wouldn't make sense to his audience and they cannot be stated in ordinary language. This is a technical matter to do with the rejection of extreme views for a non-dual metaphysical scheme. If you understand Nagarjuna then you understand why the Buddha avoided metaphysical questions. It was because he understood the answers.

Well now to my question: I somehow get scared of thinking how there was (according to science) a big bang and then I wonder what was before the big bang or where the space comes from that the universe takes up etc. I don't know why but especially these last days I'm drawn to think about it even though I know it doesn't help me in any way and even if I happen to know everything it won't change anything.

Thinking about these things is important. As a Buddhist you're attempting to transcend space-time, so thinking about what comes 'before' is useful. If you discover answers it will help you in almost every way and change everything for you for the better.

Also another thing I think of is heat death. Which again I know is a story made up by science and then I ask myself is it really worth to do anything, live, help etc. anybody if in the ultimate end everything will be gone and does that maybe imply that all beings will reach paranirvana?

The Ultimate can never go anywhere and as this is what you are neither can you. The heat-death of the universe is a regular event and of no consequence. As for whether all beings reach paranirvana, I suspect there may be two ways of looking at this.

And just like these questions seem metaphysical and paranormal I feel like the idea of rebirth and paranirvana is also somewhat scary to think about and is as well somewhat metaphysical.

It can be scary at first, but in fact there's no downside. Inevitably these ideas are metaphysical. Any fundamental theory is metaphysical. But don't imagine Buddhist metaphysics is as hopeless and pointless as the academic discipline.

I wish I could give up all these unnecessary thoughts which cause suffering to me. Also I wish science wouldn't go as far as trying to explain everything.

The practice is the medicine and cure for your problem, and it is a science. It may be called the science of Yoga and it meets Popper's criteria for a science.

I think you only need to keep studying and practicing and all these issues will disappear or be resolved.

Fear is something of nature and arises in nature, nature conceives the entirety of the universe and in that types of fear based on not knowing how it's done.

This fear is here obviously based on the ignorance element and has ignorance as a requisite condition, whatever the perfected knowledge is, it would not be not a ground for such a fear as it is antithetical to ignorance.

So... logically there is no need to fear anything of that sort because nature has no reason to fear itself and it encompasses all things, in other words we may be caught up in a war but nature always wins as it's merely here fighting itself.

What i mean is that it's not like nature is going to turn out to be a big disappointment or something like that not to say that there is no disappointment in nature but that too is delusion based as disappointment requires expectations and expectations require an unknown.

Sometimes our need for control reaches a tipping point, and becomes counterproductive in that it gives us more pain than relief.

Maybe at some point in your life, control and predictability was necessary (it usually is to some degree). Now it seems that the tipping point has been reached and clinging for control demands more than it gives.

What is worse, anicca or control? What is required for nekkhamma, and how does it compare to the requirements for remaining in control?

There comes a time when, Vāseṭṭha, after a very long period has passed, this cosmos contracts. As the cosmos contracts, sentient beings are mostly headed for the realm of streaming radiance. There they are mind-made, feeding on rapture, self-luminous, moving through the sky, steadily glorious, and they remain like that for a very long time.

There comes a time when, after a very long period has passed, this cosmos expands. As the cosmos expands, sentient beings mostly pass away from that host of radiant deities and come back to this realm. Here they are mind-made, feeding on rapture, self-luminous, moving through the sky, steadily glorious, and they remain like that for a very long time. - DN 27

This is what the pali texts say on the expansion-contraction.

I don't have much else to say but you do seem a bit confused by technical terminology such as 'nibbana', 'space', 'big bang' and etc; most people are confused about these things and of those who claim not to be confused many have contradictory views.

Perhaps if you look into the usage of the words 'all', 'world', 'origination of the world' and 'cessation of the world' in the discourses, perhaps it would make things a bit more clear or at least send you down the right rabbit hole.

Do you have any thoughts on this?

Thoughts are impermanent and unsatisfactory.

Your worries are actually internal, so turn your attention inside first before dealing with the external. Deal with external perceptions later. The heat death of the universe is not an immediate concern. What is immediately available to all of us is the breath. Simply counting breaths shifts focus away from desire and aversion for the world. Counting breaths is both easy and difficult. After decades, it is still a critical part of my practice.

So count the breaths, hold onto the count and let the heat death of the universe arise and fall away on its own.

MN10:2.1: “Mendicants, the four kinds of mindfulness meditation are the path to convergence. They are in order to purify sentient beings, to get past sorrow and crying, to make an end of pain and sadness, to end the cycle of suffering, and to realize extinguishment.
MN10:3.1: What four?
MN10:3.2: It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.3: They meditate observing an aspect of feelings—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.4: They meditate observing an aspect of the mind—keen, aware, and mindful, rid of desire and aversion for the world.
MN10:3.5: They meditate observing an aspect of principles—keen, aware, and mindful, rid of desire and aversion for the world.

OP: I know that the Buddha didn't answer metaphysical questions since it made no sense to him. He wanted to afaik limit/remove suffering as much as possible.

No. The Buddha did not answer metaphysical questions because it confuses and bewilders the questioner.

You are confused now, and it makes you scared and gives you suffering.

The Buddha already predicted that in AN 4.77:

"Conjecture about [the origin, etc., of] the world is an unconjecturable that is not to be conjectured about, that would bring madness & vexation to anyone who conjectured about it.

This is what you're experiencing now. Confusion caused by thoughts about the metaphysical nature of the world.

OP: I don't know why but especially these last days I'm drawn to think about it even though I know it doesn't help me in any way and even if I happen to know everything it won't change anything.

The Buddha did not discuss metaphysics also because it is not useful. That is exactly what you have written here. It won't help you in any way and it won't change anything. It is completely useless.

The Buddha taught in MN 63:

"It's just as if a man were wounded with an arrow thickly smeared with poison. His friends & companions, kinsmen & relatives would provide him with a surgeon, and the man would say, 'I won't have this arrow removed until I know whether the man who wounded me was a noble warrior, a brahman, a merchant, or a worker.' He would say, 'I won't have this arrow removed until I know the given name & clan name of the man who wounded me... until I know whether he was tall, medium, or short... until I know whether the shaft with which I was wounded was that of a common arrow, a curved arrow, a barbed, a calf-toothed, or an oleander arrow.' The man would die and those things would still remain unknown to him.

It is more useful to remove the poisoned arrow i.e. end suffering, rather than think about where the arrow came from, who shot it, what kind of arrow it is etc.

Also, why does metaphysical speculation lead to madness?

It's because it's outside our range of senses (including thought and mind). So, you can never completely understand it.

This too, the Buddha taught in SN 35.23:

The Blessed One said, "What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All. Anyone who would say, 'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range."

Physics - this is possible to theorize and prove. For e.g. Einstein's Theory of General Relativity can be proven by the perihelion precession of Mercury, deflection of light by stars, gravitational waves, gravitational lensing etc. It is also useful - for e.g. Theory of General Relativity has been used in the application of Global Positioning System (GPS) satellites, to compensate for time dilation.

But metaphysics? It's impossible.

Then you may ask, why do some other religions or philosophers discuss and debate about metaphysics extensively? The answer for this comes in Udana 6.4 (parable of the blind men and the elephant).

OP: I somehow get scared of thinking how there was (according to science) a big bang and then I wonder what was before the big bang or where the space comes from that the universe takes up etc.

If you fear something where there is nothing to fear, it means you are holding a false view about something. You need to let it go. As the Buddha has taught in Dhammapada 22:

317. Those who see something to fear where there is nothing to fear, and see nothing to fear where there is something to fear — upholding false views, they go to states of woe.

There's nothing to fear about the universe.

OP: Also another thing I think of is heat death. ... if in the ultimate end everything will be gone and does that maybe imply that all beings will reach paranirvana?

Parinirvana is not the same as non-existence. It is also not the same as existence.

This is discussed in many suttas like SN 44.6, SN 44.8, SN 44.11, SN 22.86, AN 10.95 etc.

The Buddha has never declared whether the Tathagata (Buddha) exists or does not exist after death.

OP: And just like these questions seem metaphysical and paranormal I feel like the idea of rebirth and paranirvana is also somewhat scary to think about and is as well somewhat metaphysical.

All the confusion about rebirth and parinirvana and what happens to beings can be answered by SN 22.86:

"What do you think, Anuradha: Do you regard form as the Tathagata?"

"No, lord."

"Do you regard feeling as the Tathagata?"

"No, lord."

"Do you regard perception as the Tathagata?"

"No, lord."

"Do you regard fabrications as the Tathagata?"

"No, lord."

"Do you regard consciousness as the Tathagata?"

"No, lord."

"What do you think, Anuradha: Do you regard the Tathagata as being in form?... Elsewhere than form?... In feeling?... Elsewhere than feeling?... In perception?... Elsewhere than perception?... In fabrications?... Elsewhere than fabrications?... In consciousness?... Elsewhere than consciousness?"

"No, lord."

"What do you think: Do you regard the Tathagata as form-feeling-perception-fabrications-consciousness?"

"No, lord."

"Do you regard the Tathagata as that which is without form, without feeling, without perception, without fabrications, without consciousness?"

"No, lord."

"And so, Anuradha — when you can't pin down the Tathagata as a truth or reality even in the present life — is it proper for you to declare, 'Friends, the Tathagata — the supreme man, the superlative man, attainer of the superlative attainment — being described, is described otherwise than with these four positions: The Tathagata exists after death, does not exist after death, both does & does not exist after death, neither exists nor does not exist after death'?"

"No, lord."

"Very good, Anuradha. Very good. Both formerly & now, it is only suffering that I describe, and the cessation of suffering."

Also SN 44.6 is useful.

OP: I wish I could give up all these unnecessary thoughts which cause suffering to me.

Yes! You need to give up unnecessary thoughts, for the reasons already explained above.