Complex sentence: Returning to Europe, he studied architecture in Paris (with J. F. Blondel) and spent five years in Italy, Then in 1755 he returned to England and established an architectural practice in London.
Split into simpler sentences: Returning to Europe, he studied architecture in Paris (with J. F. Blondel) and spent five years in Italy. Then, in 1755, he returned to England and established an architectural practice in London.