Complex sentence: Sing describes his childhood: he buys a Buddhist Palm manual from a beggar and trained himself to be a martial artist; but, when he tried to defend a mute girl from bullies, he was beaten up and humiliated.
Split into simpler sentences: Sing describes his childhood: he buys a Buddhist Palm manual from a beggar and trained himself to be a martial artist. But when he tried to defend a mute girl from bullies, he was beaten up and humiliated.