I’m sorry you are feeling so sad and lonely. At 20, you should be enjoying life. It must feel terrible to feel so dejected and alone. You do have my sympathy.
That being said, the only one who can change this situation is you. Sitting in your room and wishing someone would show up to be your friend and love you doesn’t help. To find friends, you have to be willing to get out there and look.
You live in the largest city in Brazil. One website lists 421 different attractions! There are lots of places to go and things to do there. If you’re not in school, start taking some classes. If you aren’t working at a job that puts you in contact with other young people, start thinking about changing your job. In your free time, volunteer at a museum or the zoo or get involved with sports, music, or theater. Start doing things you love to do that involve other people who have the same interests and friendships will follow.
No, it won’t happen instantly. But if you start making a sincere effort to connect with others, you’ll feel better about yourself. And just being more active will give your self-esteem a boost.
I wish you well.