Problem

I've learned English for a long time but I had no improvement in my listening and speaking (so far). I can't understand a native speaker even if they write to me... I don't know why.

So far > at the present moment

Dear Yara! I suggest you to listen to English speaking radio stations on the internet, podcasts and random videos on youtube. Little by little you will get the feeling for the listening skill you need and as to your speaking skill, you should find a partner to help you practice through a voice chat on Skype or MSN. Try finding someone here that is patient enough to help you improve it. I wish you all the best.