Before you start please remember that:
English is English
It is not French, Italian, Chinese, Swahili, Spanish or any other language. You cannot expect that one verb form (tense) in the English language will be the exact equivalent of a verb form in your own language.
English verb forms are relatively easy to form but sometimes it is difficult to know when to use one form or another. It is important to get to know the basics of English Grammar but please do not get obsessed with grammar. The most important part of learning a language is the practical day to day understanding and communicating in English
Beware of having a non-native English teacher they could possibly make the same wrong assumptions about the use of language as you! But not all native English people will know why they use one verb form or another ……… but they will use grammar correctly and will know when you use the wrong form. Receiving a good model of English is very important. Try looking at this article Is Grammar Important .. ? to see another viewpoint on the importance of English grammar