You need to speak more and listen more. Have lots of conversations with native speakers. Listen and notice what people say often. Find a few tv shows, podcasts and movies and listen to them over and over again. Repeat what you hear. Ask someone if you are saying it correctly. If not ask them what is a better way to say it. Making mistakes is part of the learning process. Even native speakers make mistakes!

The biggest thing to do is simply to speak more. If you know all of the rules and can remember them when writing, then the problem is you cannot use them as quickly as you need when you're speaking. The best way to improve the speed at which you recall these rules is to use them; you start to understand what sounds correct and what doesn't and, over time, make fewer and fewer mistakes.

I asked this question from one of my partners, she speaks English like natives and I really wish to speak English like she. she said that, English is not a collection of grammer rules, while it is a collection of phrases. she also advised me to watch series rather than movies. and what I have tested recently and it was beneficial for me was that, watch one lecture of ted talk for several times until I memorize all of the speech.