Its not normal i use to have the same problem put with different phone i changed battery oh wait you'r phoone used or new if its used then its the battery if its new then i dont know Lol
Now you have two cards the one on the cpu and the one you just purchased what you have to do is go to you'r desktop and right click ,Display there should be 3 option's choice the third one that will use both the cpu graphic and the video card you purchased .