1) Ofcourse, i pay in cash for things that i buy
2)Yes, i had lended money to my friends
3)sometimes i had borrowed
4)вопрос не очень понятен (сохраните вы покупку купить что-то что ты хочешь. как -то так)
5)there are many teenagers who waste their,and not only their, but thir parents money for things that they not really needed.But, there are teenagers who waste their money on good things. e.g For guitar, for books that will help them in future, and another things
6)there are many clothes which price is big.But you now, it depends on Money which the family have. If it's a poor family, i think that if smth cost for example 1000 rubles it may be a big price for them,and if it is a rich family, they may consider that it is penny
7)My day depends on my study.