1.I think that sports activities are the best for people my age. Teenagers rarely go out*. They are couch potatos. They use computers / play computer games (way) too often. Sports classes can affect our health positively / in a positive way. We learn good habits.** We can develop our bodies by playing sport games.
*go out = wychodzić w celu rozrywkowym
**nie sądzę żeby habits występowało w kolokacji z learn, ale też nie jestem pewna jak to zmienić
2. There are many differences between modern schools and those from the past. Firstly, schools are far better equipped now. There are computers and multimedia projectors* that wouldn't be found there in the past. Schools are safer now, because surveillance cameras** are used (installed?). Moreover, teachers are better educated than in the past. Schools offer more extracurricular activities***.
* z tego co wiem, ta rzecz nazywa się po angielsku overhead projector
**surveillance cameras = kamery monitoringu (surveillance samo w sobie to pilnowanie przez policję/ochronę)
***extracurricular activities = zajęcia pozalekcyjne (dodatkowe)
no i past jako rzeczownik o ile wiem zawsze idzie z articlem (zauważ różnicę między THE past/ A past)