It Is A New Start

It is sunny today,but unfortunately, I am in a bad mood.
Now, I have an account with (of) italki, following my roommate's advice, (.) and the most important thing for me is to be persistent with my language practice. (persist in practicing.) I hope it will be a (I can have) wonderful experience here and that I make some interesting friends.I am really looking forward to the trip.
Recently, I have become (am) interested in painting,taking photos(still learning)and exchanging postcards with strangers. If you have any interest, (tnterest,) please get in touch. (just tell me.)

We usually use initial capitals in the title of an essay. You generally have 'an account with'... for example.. your bank (not of). You can join your second and third sentences as you already have the conjunction 'and'.so just need a comma after 'advice'. You writing is of a good standard and I have just suggested a few more native ways of expressing some of your thoughts.

It is a new start

It is sunny today, but unfortunately I am in a bad mood.
Now I have an account on italki following my roommate's advice. And The most important thing for me is to persist in practicing. I hope I can have wonderful experience here and make some interesting friends. I am really looking forward to the trip.
Recently I am interested in painting, taking photos (still learning) and exchanging postcards with strangers. If you have any interest, just tell me.

Don't forget to put a space after commas and periods. We normally don't begin a sentence with a conjunction (and, but, or, etc.). These are primarily used to join two clauses within a sentence. Other than these small things, your English is very good.

It is a new start

It is sunny today, but unfortunately I am in a bad mood.
Now I have an account of on italki following my roommate's advice. And the most important thing for me is to persist in practicing. I hope I can a have wonderful experience here and make some interesting friends. I am really looking forward to the trip.
Recently, I am interested in painting, taking photos (still learning) and exchanging postcards with strangers. If you have any interest,  just tell me.