C’mon do your own homework. If we correct your mistakes, you won’t develop any useful skills.

Here’s what I’d recommend you:

Gay marriage should be legalized because banning it is inhuman and uncivilized. Our Constitution gives us many rights and liberties. One of the basic freedoms is the pursuit of happiness of which gay people are deprived. They cannot marry people they are in love with, and it makes them unhappy. This ban violates their freedoms and liberties. While others can choose whom they want to marry, same sex couples suffer.

And don’t forget to include a strong thesis statement in your essay.

I dunno I like your essay as it is. Add me as friend on this community and I will add you too.

Doesn’t Word underline all those typos? First, you should check it using some online software. Have you ever tried grammarly.com – an online grammar checker? It might help.

Some more resources that give useful advice on proofreading:

https://owl.purdue.edu/owl/general_writing/the_writing_process/thesis_statement_tips.html
http://writingcenter.unc.edu/handouts/editing-and-proofreading/

Good luck with your essay and have a nice day!