Raymond Murphy has an excellent book for learning the tenses (Intermediate English Grammar, Cambridge). Let's see how he deals with DOES (present simple) and IS DOING (present continuous).
Next, Raymond takes on DID (past simple) WAS DOING (past continuous)
Perhaps the trickiest distinction is between DID (past simple) and HAVE DONE (present perfect). Please remember, past simple is for finished actions that happened at a moment in the past. Present perfect is a past action with a result in the present, or for a past action/state that continues to the present moment. Signal words for past simple include moments in the past (yesterday, 3 years ago, January the 15th, at 3:30, when, last week, last month). Signal words for present perfect are usually words that demonstrate a connection between the past and present moments (yet, already, just, for, since) or words that indicate an unfinished period of time (ever, never, so far, today, this week, this month, this year)
Unfortunately, present perfect comes in two different forms: simple (HAVE DONE) and continuous (HAVE BEEN DOING). While the latter is rare, it is frequently necessary when we say how long a verb has been taking place.
In my opinion, a solid grasp of the tenses is absolutely crucial for those who wish to reach an intermediate level. Let's start with an overview of all 4 present tenses. In future classes, we will put the theory into practice.
Time to put the theory into practice: let's try an exercise.
Let's examine the passive forms of the tenses
Now let's revise those tricky irregular verbs
In the following lesson, we see how questions are formed in different tenses
Let's revise those past tenses with a few more exercises