Complex sentence: Toronto has one of the highest population of Italian immigrants in North America, many of these immigrants are second and third and occasionally fourth generation immigrants so very few are actually fluent in Italian but many still consider themselves Italian by blood.
Split into simpler sentences: Toronto has one of the highest population of Italian immigrants in North America. Many of these immigrants are second and third and occasionally fourth generation immigrants so very few are actually fluent in Italian but many still consider themselves Italian by blood.