Complex sentence: He is most famous for his hit "What Are Words", which reached number 1 in Sweden and Norway; it also charted in Denmark and made it to number 83 on Billboard Hot 100.
Split into simpler sentences: He is most famous for his hit "What Are Words" a big hit for him in Sweden and Norway where it reached number 1. It also charted in Denmark and made it to number 83 on Billboard Hot 100.