Hi! Who uses menstrual cups?

Hi! Who uses menstrual cups? Explain to me how to insert the cup so that it doesn't leak? I've tried every way! I have two sizes of cups. The small one doesn't open up in me. The big one opens up. I insert it tightly until the end. But it still leaks! I spent 700 rubles on these cups, is it not worth it? For the second month I'm struggling and nothing works ? What am I doing wrong... Maybe I'm doing something wrong because it leaks. Or maybe the size isn't right?