Complex sentence: He travelled to London to complete the music, learning English to be better capable to follow the libretto, before the successful premiere of the opera; however, he destroyed his health in the process and died in London on June 5,1826.
Split into simpler sentences: He travelled to London to complete the music, learning English to be better capable to follow the libretto, before the premiere of the opera. However, in the process, he destroyed his health and died in London on June 5,1826.