Complex sentence: There he started composing and arranging music for Iranian pop singers he became famous as a composer for the songs he composed for the famous Iranian singer Moein he composed many songs for him and played violin in his concerts and learned the art of singing from him.
Split into simpler sentences: There he started composing and arranging music for Iranian pop singers. He soon became famous as a composer for the songs he composed for the famous Iranian singer Moein he composed many songs for him and played violin in his concerts and learned the art of singing from him.