During the last week I bought coins and they almost immediately fell by 10-15%, and today early in the morning I saw how they fell by another 15-20%. How long will it last?., and whether I should sell for what I have. I wouldn't want to be left with empty pockets. 
no, you don't need to panic and despair because this is the right time to buy some cheap coins on the market. if you are worried about seeing the current market downturn and you want to sell coins, then the profit you get is not big but you get loss, now you just have to buy coins and HODL. be patient, we will soon see Bitcoin going up again.