Hebrew speakers find the subject of Tenses very problematic. Things are simpler in Hebrew. There is only one Present, one Past and one Future.
Continuous Review and Practice are highly recommended. Exercises assigned as homework or class activity have to be checked in class, problematic issues have to be discussed and mistakes have to be corrected and explained thoroughly.
The following exercise can be used for review of the Verb.
If only I (know) ————————- last week that he (go) ———————- (quit) —————- his job, I (may stop) ——————————– him. However, his plan (must make) ————————– while I was away on holidays. I (hear) ——————- about it only when I (come) —————- back, but then it was too late.
had known, was going, to quit, might have stopped.
The first sentence is a Conditional Sentence. The keyword is IF. The Condition is the Third Condition since it refers to the Past (keyword: last week). The sentence is a complex sentence. The Condition appears at the beginning (If I had known – Past Perfect) and the Result appears at the end (I might have stopped him – Future Perfect Conditional). Between the Condition and the Result, we have two verbs that are not part of the condition from the point of view of structure (Condition and Result). The verbs are in the Be going to Form (was going to quit: a structure often used to describe an action in the Future. In a text in the Present we will use the version of the Present: am / are / is going to – referring to a real Future, still ahead of us. In texts in the Past, like in this text, we will use the version of the Past: was/were going to – referring to an unreal Future – a Future that has already become part of the Past).
must have been made
The modal Must usually means obligation, but here it means probability (כנראה). In this case, we will put have and V3 after Must. The structure is Passive since plans do not make, but are made by somebody and therefore, we add been between have and made.
Both verbs appear in the Past Simple. The keyword is When. The word when focuses on the Past in this case. The stress is on the time when the actions took place. That is why we use the Past Simple.
For more explanations, see: דקדוק אנגלי לדוברי עברית, עמ’ 145 – 149
For further practice, see The New Language Guidebook and Workbook, p 198 – 208