I understand everything but I can't speak well
your opinion is very important to me to be good at english
The English saying goes "Practice makes perfect," meaning that if you allow yourself the chance to speak English and to flex your linguistic muscles every now and then, you'll end up eventually with a quite reliable English. Just try to avail yourself of any communication opportunity that comes your way, be it online chat, skype talks, real-life meetings and what have you!
Hi :) Try watching and listening to movies and BBC podcasts .. listen again and again and try to imitate the sounds you hear over and over .. soon enough you'll be able to bring the correct accent .. and you'll be able to say different common phrases so easily , just like a baby that learns by listening only .
That's my advice and worked very well with me . good luck :)