I recommend you to watch her videos. She makes learning English easier especially in the grammar part. https://www.youtube.com/user/MinooAngloLink/videos

Tenses and verb forms are definitely something that differs greatly when learning English or a romance language. I think part of it is knowing the bigger picture of what you are trying to say before using past/present/future tense, as the subject itself is highly dependent upon the <em>context</em> of a statement.