Someone told me Buddha copied almost everything from Brahmanism, how accurate is that?

Brahmins ate beef & strict propogadist of evil customs which we Buddhist cannot believe from 2500 years . China is a centre for Buddhism expansion to other regions as like srilanka who spreads Buddhism to far South East region of asia. As From South Asia , brahmins were group of propogadist who were involved in massacre of followers of Buddhism. Everytime you need to find out the way how our South Asian followers were vanished from their original roots of our Buddhist culture, as they were pressured to convert & murdered. Buddhism is most infly religious beliefs of South Asian community but vanished in previous centuries. But as we know reactions follows after actions , Srilanka is one of centre still follows our traditional Buddhist culture & some South Asian also cooking towards new recipe of Buddhism in India.

Everything is an incarnation of something else. If you read the upanishads and Bhagavad Gita those go really well with the Dhammapada. Gautama was from Indian where it left and went to China and Japan and eventually the world. But naming like we do when we categorize has its limits.

Buddha came around 500-800 BC and Vedanta originated about 100 BC - 1100 AD. So in fact its the other way around.

If you read and understand these philosophies, you will find that Advaita Vedanta is a copy and paste of buddhist philosophy with some minor changes. Most of the terminology is also same.

Only difference are some abstract terms in buddhism such as consciousness, karmic structure are replaced with terms paramatma and atma etc. Rest is all same.

In fact, Adi Shankaracharya is considered by many as cryto-buddhist (or closet/ hidden buddhist) who changed the bhakti and ritualistic nature of Hinduism and turned it into spiritual system/ meditative system.

Someone (I forget who -- Paul Carus perhaps) drew an analogy with Christianity -- saying that Buddhism is a reformation of Brahmanism, like Christianity is a reformation of Judaism.

In my opinion, the doctrines might seem similar superficially, in that they inevitably have some words in common -- a common language or vocabulary, the vernacular. If Christianity and Judaism both use the word "God", here you say that Buddhism and Hinduism both use the word "mind". I don't understand that to mean that it's "copied" though. If I paint an original picture, and you paint an original picture, and we both use the same paints -- we're both using the same paints (the same words) to create our pictures, but that doesn't mean that we're copying each other's pictures.

dyana (meditation)

Forms of meditation were practised in China too at about that period -- without I think being copied from Hinduism.

I don't assume it (meditation) is specifically "Hindu" rather than "human".

Sakyamuni did study under other contemporary teachers, before he attained enlightenment -- he found their teachings insufficient, though.

dharma became dhamma

It's a very general word, meaning something like "doctrine" or "reality" or "the way things are".

Every doctrine has (or is) dhamma, by the definition of the word, that doesn't mean they're copied from each other.

ideas of reincarnation

I'm not really familiar with Hindu ideas of reincarnation, I think the ideas might be dissimilar though.

I presume that the Buddhist doctrine of anatta (the non-existence of a permanent self) makes it unlike the Hindu idea.

daya (compassion)

Again, IMO this (Compassion) is a human theme: not specifically Hindu or copied from Hinduism.

How much did Sakyamuni reinterpreted on Brahmanism and how much is disinformed?

There are many suttas in which the Buddha interacts with (talks with) Brahmins -- sometimes to criticise their behaviour, or to explain why and how his (Buddhist) dhamma is different from theirs (early Hinduism).

I think it's truer to say that it's "reinterpreted" rather than "copied". Even so that reinterpretation (i.e. contrasting Buddhism with Hinduism) may occur especially when talking with Brahmins.

There's a Wikipedia article Buddhism and Hinduism -- I think it's an OK article, not brilliant -- at a minimum it begins to illustrate how many similarities there are, and how many differences: more than it's easy to answer fully, here.

I've also heard the opposite, for what it's worth -- that some aspects of (later) Hinduism are copied from influenced by, or in response to, Buddhism (and/or Jainism). I don't know any details of that though; only that Hinduism continued to evolve after Buddhism started. Hindu synthesis and smriti says:

The smriti texts of the period between 200 BCE and 100 CE belong to the emerging "Hindu Synthesis", proclaiming the authority of the Vedas while integrating various Indian traditions and religions. Acceptance of the Vedas became a central criterion for defining Hinduism over and against the heterodoxies, which rejected the Vedas.[17]

The so-called "Hindu Synthesis" emerged during the early Classical period (200 BCE – 300 CE) of Hinduism.

I think Sakyamuni was earlier (Wikipedia says "c. 563/480 – c. 483/400 BCE"), with Jainism founded maybe one generation before that.

Buddhism could, perhaps more accurately, be seen as a "reinterpretation" of Jainism rather than Hinduism (see "Jainism and Hinduism", and "Buddhism and Jainism"), perhaps only in that before his enlightenment he tried various austere/ascetic/extreme (Jain-like) practices, before eventually abandoning them as unprofitable and practicing and teaching "the middle way" instead.

About the core unique teachings, the suttas report the Buddha saying:

Pubbe ananussutesu dhammesu cakkhuṃ udapādi, ñāṇaṃ udapādi, paññā udapādi, vijjā udapādi, āloko udapādi

Vision arose, insight arose, discernment arose, knowledge arose, illumination arose within me with regard to things never heard before...

Dhammacakkappavattana Sutta

Dyana meditation is basically keeping your focus on one object. Various forms of it can be found in many religions. There's nothing exceptional about it. Even christians/muslims praying to a God is a type of concentration meditation that could lead to the first Dyana. In that case, the object of focus is conceptual or fictional.

In Buddhism also you can find types of Dyana meditations as they are useful methods of developing concentration and subduing defilements. But what makes Buddhism exceptional is Vipassana meditation. This meditation is not found in any other religion. Then there are so many unique teachings like the four noble truths, the noble eightfold path, most of the teachings in the sutta, abhidhamma, vinaya pitakas that amount to 84,000 teachings.

So if someone claims that the Buddha copied almost everything from Yoga, it only speaks of his lack of knowledge in Buddhism.

Prior to the Buddha (born 563 or 480 BCE), was the historical Vedic religion (1750 - 500 BCE), followed by the shramanic movement (500 - 200 BCE), and the beginnings of the Upanishadic movement within Hinduism (500 - 200 BCE). Buddhism is also considered to be part of the shramanic movement. Vedanta came later as part of Classical Hinduism (200 BCE - 1100 CE). You can find this information here.

Prince Gautama, after leaving home, followed the shramanic traditions which were based on asceticism. Jainism was one of the major shramanic traditions at the time. The Pali Canon (DN2) has descriptions of various shramanic teachings at the time (Pūraṇa Kassapa, Makkhali Gosāla, Ajita Kesakambalī, Pakudha Kaccāyana, Sanjaya Belatthiputta and Mahavira). These teachings may or may not be compatible with the Vedic religion at the time.

Gautama tried to follow the different teachings at the time (Vedic and shramanic teachings) and found that it did not lead to the goal that he sought. And you know the rest of the story of how he found enlightenment and started teaching.

Hindu religious scholars today like to do two things. The first is to place all these different groups under the umbrella of Hinduism, sometimes including religions that do not accept the authority of the Vedas like Buddhism and Jainism, but sometimes not. This is often used to generalize that all concepts in Hinduism today are older than Buddhism, when in fact, not all concepts in today's Hinduism come from the ancient Vedic religion. On the other hand, Buddhist scholars tend to describe Classical Hinduism as "Hinduism", while they describe the Vedic religion as "Brahmanism".

By grouping everything together, the Hindu religious scholars hide the fact that Buddhism (and other shramanic schools) had indeed influenced Vedanta and Classical Hinduism. It is well known that the founders of Advaita Vedanta including Gaudapada and Adi Shankara, were influenced by Buddhist philosopher Nagarjuna's Mula-madhyamaka-karika and Buddhism. This can be seen in Hinduism.SE questions here and here.

The second thing that Hindu religious scholars like to do is misrepresent the age of a scripture. The Brahma Sutras or Vedanta Sutras which includes criticism of Buddhism (see this question) is claimed to be much older than the Buddha by Hindu religious scholars (see here). Meanwhile, in the Wikipedia article on this text, we can see that most historians and academic philosophers have the opinion that the Brahma Sutras or Vedanta Sutras come at least two centuries after the Buddha. The same applies to other Hindu texts like the Bhagavad Gita and certain Upanishads (Kena, Katha, Isa, Svetasvatara, Mundaka, Prasna, Mandukya), according to the timeline of Hindu texts.

This again shows that many writings that come after the Buddha, would most likely have experienced influence from the Buddha's teachings, but would be misrepresented by Hindu religious scholars as being far older than the Buddha.

While the ancient Vedic religion was based mainly on sacrifice and worship to the Vedic gods, I would guess that ideas like dhyana and samadhi come from the shramanic movement, which include ascetics who may or may not accept the authority of the Vedas. It is also likely that shramanic ascetics may have influenced each other, just as the Buddha learned some things from other teachers like Alara Kalama and Uddaka Ramaputta, although they did not achieve the Buddha's level of enlightenment before the Buddha did. It is well known that the Buddha discovered Vipassana meditation but not Samatha meditation (see this answer). Samatha meditation existed before the Buddha's time.

Apart from that, there are also other concepts that are simply common human themes that can be found in many cultures around the world, or are common words found in many languages. Examples include karuna (compassion), atma or atta (self), maitri or metta (friendliness).

Here are some major doctrinal differences between Buddhism and Classical Hinduism:

• The middle way between eternalism and annihilationism (Hinduism subscribes to eternalism of the self) - see this answer
• The self is not eternal, not standalone and not independent - see this answer, and SN44.10, and contrast with Hindu BG2.24
• The self or soul does not pervade the body (unlike the Hindu BG2.17) - see SN35.85
• There is no Supreme God (unlike Hinduism) - see this answer
• The self or soul does not transmigrate (unlike Hindu BG2.22) - see this answer
• Warriors dying on the battlefield while performing their duty do not go to heavan after death according to SN42.3 (unlike Hindu BG2.32)
• Lay people eating meat that was bought dead and frozen from the supermarket is not sinful - see this answer

Centuries after the Buddha's passing, the development of Buddhism and Hinduism did influence each other. As discussed in this answer, later on, Buddhist and Hindu philosophy influenced each other to produce Advaita Vedanta and Indian Mahayana Buddhist philosophy. Also, Tibetan Buddhism have adopted some Hindu deities. On the other hand, there has also been debates in later times between Hindu and Buddhist scholars (see this question).

It must be clear that the Buddha's unique contributions that cannot be found in Hinduism and other religions, are anatta, vipassana, dependent origination (pratityasamutpada) and the middle way between eternalism and annihilationism (see this answer).

Furthermore, anatta is the irreconciliable difference between Buddhism and Hinduism, as stated by eminent German indologist Professor Helmuth von Glasenapp in his essay "Vedanta and Buddhism: A Comparative Study":

Nothing shows better the great distance that separates the Vedanta and the teachings of the Buddha, than the fact that the two principal concepts of Upanishadic wisdom, Atman and Brahman, do not appear anywhere in the Buddhist texts, with the clear and distinct meaning of a "primordial ground of the world, core of existence, ens realissimum (true substance)," or similarly.