Tell your foreign friend what opportunities a teenager in your country has to express him/herself. remember to say: what teenagers look like ; what music they like; what groups they can join. вот что получилось: russian teenagers have many ways to express the him/herself. in russia there are many subcultures such as bikers, hippie, punks, ravers and each teenager can join them. each subculture has its own music,own clothes style, manners of behavior. but if none of subcultures is not suitable teenager he or she can select music,clothes style,manners of behavior on its own will. the most popular types of music in russia it is pop music, techno,rock, rap, r& b. исправьте ошибки и посоветуйте что добавить.
Правильнее The most popular types of music in Russia ARE pop music, techno,rock, rap, R&B.
Russian teenagers have many ways to express the him/herself.
Тут не надо ставить the. В следующем предложении, думаю, лучше поставить вместо each every.
В принципе, все по существу, просто интереснее, какой объем) если скажете, сколько приблизительно надо добавить предложений, я постараюсь