Problem in switching most games to external graphics

I'm using an aspire e5 550g laptop. The internal graphics is AMD Radeon R6(1gb) and the external graphics is AMD Radeon R7 M265(2gb). Eventhough I configure my games to high performance in Switchable graphics, most of it works only in the internal graphics(Radeon R6). So far I only played the game Far cry 4 using external graphics. How do I fix this problem?