Biological essentialism is athe belief that an individual's personality or some specific quality is an innate and natrural essence, rather than changing by circumastances.

The sSexual orientation is caused by a complex interplay of genetic, hormonal, and environmental influences.

There areis some researchs that shows that they born from this way.people are born with a specific sexual orientation.

1) You can either say "There is some research..." or "There are some studies...", but you can't say "There are some researchs."
2) I changed the end of your sentence to make it more specific, since you didn't identify before in your paragraph who "they" is and what "born from this way" means.

One is TAn example of this is twin studies.

Scientists have found that identical twins are more likely to have the same sexual orientation than non-identical twins.

Another one is boys were surgically reassigned female, but they still consider themselves as men.

This sentence sounds odd because it doesn't really sound like it fits here. Do you want to try to rewrite it and I can correct it?

Apparently. there are more studies on gahomosexuality than other typesexual orientations.

But what is interesting inInterestingly enough, the questionnaire ireveals that many gays are reluctant to admit it.

What does "it" refer to here? Childhood gender nonconformity? Or something else?

Because tThey believe that if they take female dressdress in a feminine way, they will face more peer pressure, and can notwill not be able to attract the same sex.

Be careful when you start a sentence with the word "because". Most of the time, it will sound odd.

I think it sounds better if you combine this sentence with the last sentence. Obviously, if you combine the two sentences, you can leave the word "because" in, since that will be your transition word.