Hi Daria I am not sure there is a quick & easy answer. These tenses will be particularly challenging for natives of Slavic languages because they do not exist in your language. Roughly speaking past prefect & past prefect continuous are used to reference one past event from another past event. Example: Before you visited me yesterday, I had been working on my project. When I teach them, I try to help students focus on "when" or what "situations" we would use a particular tense. Often you will notice words like "Before", "When", & "Since".. which are used to reference prior events. It will take time for you to observe and get used to this. I would recommend you observe the examples in the 2 sites I am posting below..and then try watching some Tv Shows/Movies/Youtube you enjoy and look out for their use. I supposed you would need to look some story about the "past" . It would be great to see the English captions (subtitles) so you can pause it if you see a past perfect /past perfect construction and review it in the context of the show. I hope these suggestions help! https://www.grammarly.com/blog/past-perfect-continuous-tense/ & https://learnenglish.britishcouncil.org/en/english-grammar/verbs/past-tense/past-perfect

Basically both past perfect and past perfect continuous have one thing in common - they both use another event happened in the past as a reference for the timeline. What is different between these two is that, for past perfect the first action finishes before the second action you used as the timeline reference. For the past perfect continuous, the first action continues until the second action.

Past perfect continuous is rather the same, it is used when we are telling a story and want to describe a continuous action in the past, if you already know how to use present perfect continuous then it is just one step back in time: I just arrived at work. Lara has been waiting for me all day When I arrived at work yesterday, I saw Lara who had been waiting for me all day

Past perfect used mostly when you are recounting a story, if you already know how to use the present perfect then it is just one step back in time, for example: I am at work now, I just realized Lara has finished all the food in the fridge I was at work yesterday that I realized Lara had finished all the food in the fridge