Original Entry in Black, Changes in Blue and Comments in Red. 

I'm a girl of 18 years, old and my name is Sigita:)

Expressing age as above is valid - just archaic (very old). Most people would say:
"I'm an 18 year old girl" 

Also, while it is an advanced subject, and definitely not expected of you, I would modify then conjunction. I would finally write the sentence as:

"I'm an 18 year old girl; my name is Sigita. :)" 

I am learning English because I want to pass my English exam, and maybe one day live in abroad. Of course, I want to make some friends who will help me. I was born in Lithuania, so my native language is Lithuanian. In my leisure time, I like to be with my friends and play VOLLEYBALL!! :)

A common mistake I've noticed with people just learning English is confusion on what exactly English infinitive verbs are. In most languages, an infinitive is just one word - in English, it is two: every infinitive verb starts with 'to.' So, when ever you use an infinitive verb form, like you did above with 'to make' be sure to add that 'to' in before the verb itself. 

This looks a little bit better ;)

I'm a girl of 18 years old and my name is Sigita:)

I am learning English because I want to pass my English exam and maybe one day live in abroad. Of course I want to make some friends who would help me. I was born in Lithuania so my native language is Lithuanian. In my leisure time i like to be with my friends and play VOLLEYBALL!! :)

I'm a girl of 18 years old and my name is Sigita:)

I am learning English because I want to pass my English exam and maybe one day live in abroad. Of course I want make some friends who help me. I born in Lithuania so my native language is Lithuanian. In my leisure time i like to be with my friends and play VOLLEYBALL!! :) Also i would like to learn Russian and German