Complex sentence: These nationalities have the chance to be presented at project days that the school organizes called, "The world culture days", which are held every year by second graders from the school, at "Casino Cosmopol" in Gothenburg city.
Split into simpler sentences: These nationalities have the chance to be presented at project days that the school organizes called, "The world culture days". These are held every year by second graders from the school, at "Casino Cosmopol" in Gothenburg city.