I have been meditating by myself since 2015 but nothing worked for me

I get only tingling sensation on my forehead & constant buzzing sound.

Do not give too much importance to this for the moment, i.e., do not consider it as good and crave for it or do not consider it bad and be averse towards it. Just keep your equanimity knowing they arise and pass.

Besides, I have not gotten any slight improvements in my behavior.

Behaviour doesn't change overnight. In the past, given 10 situations you react in an unwholesome way. If this changes to 9 out of 10 or 8 out of 10 situations, this is an improvement. So if there is a slight improvement also, this is immaterial, so just keep doing what you are doing.

Also there could be no improvement because you are practicing wrong or the techniques you are practicing might not be suitable to you.

How to meditate finally? That one method that can bring peace and calmness to me.

When you meditate calmness and insight grows. So do both:

• Anapanasati, and
• Satipatthana

When to do ?

Whenever possible. But this might help:

• 5 - 10 minutes after waking up (awake but just not yet out of bed)
• until you fall asleep (in bed but not yet fallen asleep)
• 1 hour session in the morning
• 1 hour session in the evening / night

Prerequisites.

The main thing is morality hence contemplate on morality and make a determination to be moral. In addition the following may would be helpful:

• Develop some faith in the practice so you would be earnest in the effort you put into it
• Develop gratitude towards the Triple Gem, otherwise you will not have got the chance to practice
• Develop a sense of urgency to practice, think this might be the last chance
• Develop Metta

How much to do?

Generally do 2 session of about 1 hour or more formally. Use this as a booster to continue the practice during daily activities. Ultimately it is being mindful during daily activities that gives the real results.

In doing 2 sessions, if one session is not productive then the other might be more productive. At the start of the session, you might not be meditating much hence it should be long enough to settle down and put some solid practice.

This little plant of Dhamma requires service now. Protect it from the criticism of others by making a distinction between the theory, to which some might object, and the practice, which is acceptable to all. Don’t allow such criticism to stop your practice. Meditate one hour in the morning and one hour in the evening. This regular, daily practice is essential. At first it may seem a heavy burden to devote two hours a day to meditation, but you will soon find that much time will be saved that was wasted in the past. Firstly, you will need less time for sleep. Secondly, you will be able to complete your work more quickly, because your capacity for work will increase. When a problem arises you will remain balanced, and will be able immediately to find the correct solution. As you become established in the technique, you will find that having meditated in the morning, you are full of energy throughout the day, without any agitation.

...

When you go to bed at night, for five minutes be aware of sensations anywhere in the body before you fall asleep. Next morning, as soon as you wake up, again observe sensations within for five minutes. These few minutes of meditation immediately before falling asleep and after waking up will prove very helpful.

...

Daily meditation of two hours and yearly retreats of ten days are only the minimum necessary to maintain the practice. If you have more free time, you should use it for meditation. You may do short courses of a week, or a few days, even one day. In such short courses, devote the first one third of your time to the practice of Anapana, and the rest to Vipassana.

Source: The Discourse Summaries by S.N.Goenka