Complex sentence: His career as a musician began in 2015, when he released his first EP, which contained the song, "How Many Times" which went on to be remixed by German duo Andhim, becoming one of Mixmag's best songs of 2015.
Split into simpler sentences: His career as a musician began in 2015, when he released his first EP, which contained the song, How Many Times. Which went on to be remixed by German duo andhim, becoming one of Mixmag's best songs of 2015.