Hello Nilay!

Below, I'll correct some little mistakes in your text, then I will explain about the site, right?!

try to write

I heard about this web site yesterday. My friend said to me. I became a member. I'm trying to learn more about italki. How can I use it? Where do I click? etc :) I have no experience in using the site yet.
As I said, I'm a city planner. This is my job currently but actually, I'm interested in being a theater ctress . When I (Always use the pronoum "I" in Capital letter) was at university I played a role in the theatre. Nowadays I am still (The adverbs of time comes before the verb) playing. I'm going to drama course. I love it. I want to be a master in performing arts. But for this I must pass on an English exam. This exam named YDS (Foreign Language Exam) is performed in Turkey. I'm having trouble. I can't write and speak very well. I want write something always for improve my English.

Well Nilay, In my opinion you should look for learn more about grammar, to be more confident about the rules and how to use some correct words and mainly the position of each word. You write well, don't give up! It only a matter of time and I'm sure you will reach all your goals!

I can try to help you having some conversation if you want! 
Have a nice day! 

try to write

I heard about this web site yesterday. My friend said to me. I became a member. I'm trying to learn italki. How to use it? Where do I click etc :) I have no experience on how to use the site yet.
I said I'm a city planner. I am working now but actually I'm interested in theater. When i was at the university i played in the theatre. Now i am still playing. I'm going to drama course. I love it. I want to master about performing arts. But for this i must pass an English exam. This exam's name YDS (Foreign Language Exam) in Turkey. I'm having trouble. I can't write and speak very well. I want write something always for improve my English.

try to write

I heard of/about this web site yesterday. My friend told me (about it). I became a member. I'm trying to learn about italki. How do i use it/does it work? Where do I click etc? :) I have no experience on/of how to use the/this site yet.
I said I'm a city planner. I am working now but actually I'm interested in theater. When i was at university i played in the theatre. I am still playing there. I'm going to do a drama course. I love it. I want to master about performing arts (here you can either say 'master performing arts' or 'learn about performing arts. 'to master' means to become an expert, and 'learn about' means you will learn without necessarily becoming an expert). But for this i must pass an English exam. This exam's named 'YDS' (Foreign Language Exam) in Turkey. I'm having trouble. I can't write or speak very well. I want write something always for improve my English. (This sentence needs to be reworded. Something like 'I want to write a lot to improve my English.' perhaps.)