Sorry Vadym, your question sounds like, "I don't really understand this grammar. Can I ignore it?" We do use these forms in spoken and written English, quite often, and any speaker at intermediate level or higher knows how to use them. Lewis has given a pretty good explanation, so I suggest you get used to them and look forward to becoming an advanced speaker of English. :)

All the tenses of English tend to be used by native speakers in conversation, when the time is appropriate. The past perfect (had done, had seen, had studied) and the past present continuous (had been working, had been doing) are both fairly common tenses that I would use and expect to be used in casual conversation to describe events that happened before a certain time in the past. For example, a question I can imagine being asked at a job interview might be: "How long had you been working at the company before you decided to leave?", or "How long had you studied before you were fluent in French?".