Complex sentence: By the age of sixteen, he had a good knowledge of Hungarian, Latin, French and German, and was rapidly acquiring English, the Scandinavian languages, Russian, Serbian, and other Slavic languages.
Split into simpler sentences: By the age of sixteen, he had a good knowledge of Hungarian, Latin, French, and German. He was also rapidly acquiring English, the Scandinavian languages, Russian, Serbian, and other Slavic languages.