my first entry..

Hi, my name IS Julio Antonio AND I AM from Maceió in Brazil. I'm 22 years old and single.  I like football and THE gym. (Or, and I like going to the gym)

Hi Julio

using name's and I'm is not wrong but it reads better as above.  My opinion anyway :-)

first write

Hi, my name is Julio Antonio I am from Maceió in Brazil. I am 22 years old. I like football and I like going to bodybuilding gym.

Hi, my name is julio antonio and I'm from Maceió in Brazil. I'm 22 years old and single. I like football and going to the gym.

I'm is the same as "I am". 

Also, in the US, we don't really introduce ourselves with relationship status typically.

You can say "I like football and working out" 

first write

Hi, my name is Julio Antonio and I am from Maceió in Brazil. I'm 22 years old and single. I like football and I like going to the gym.