don't concentrate on grammar, don't do hard efforts on learning grammar rules. i advice to read many english books and listen english audio stuff, which is interesting for you. and your grammar will improve, i promise :)

Study, study and study. There's no magical recipe.

for each grammatical rule , you need to know two things: how the structure is formed and how it's used ; in other words you need to know form and use e.g. present simple tense form: the first conjugation of the verb, add s or es to the verb when the subject is third person singular use: to talk about facts which are always true and repeated habits or actions the sun rises in the morning. i always get up at six in the morning. also, you need more practice, as : practice makes perfect.

Go teach english grammar. That will force you to learn it. :P

Most people (native speakers included) see grammar as a bunch of annoying rules which must be followed. Instead, try to see the grammar rules as tools you can use to make your meaning clear.