If it's the former you might find it useful to have some sort of tuition. I'm going to hazard a guess that from the sounds of it you live in a non-English speaking country. In that case you might take a look at Skype lessons, I have used iTalki in the past to find a tutor although I recall once you buy credit on the website you have to spend it and can't withdraw it back out, which I didn't like.
If you're wanting to improve in more casual conversations you might try getting involved in some kind of social activity which is done in English. This could be meetups in your city or playing multiplayer video games online with a group.
Either way this will hopefully get you more "fluent" where you'll begin to get intuiton what is the correct way of saying something without having to consciously think about grammar rules. Unfortunately as you know there's a lot of weird rules and exceptions in English which make it a nightmare to pick up. You might also try finding some media you can enjoy more passively such as audiobooks in order to increase your exposure to the language and give you more of a feel for it. Good luck!