Everybody has strengths and weaknesses. You say that you know what you want to say, you are just finding it hard to put it on paper- that is most probably lack of vocabulary. You will get better with practice and as you get older your vocabulary will broaden as well. A great thing to do in the meantime is to read books (not just boring books, you can read anything you like as long as it's an actual book and not a magazine), and watch the news. You should watch the news for a few reasons, one being it really will increase your literary techniques and vocabulary, and another reason being it's always good to know what's going on in your country/around the world.
Because not only is it ironically stupid and contradictory sometimes, but it also has different forms. Saving time was not part of the formula for English language; no worries though, it get easier! I hope...
im finding it hard because i know what to say in my head but i just can't put it down on paper
It's easier if you read a lot.
It's not hard for everyone.
i do watch the news though