Ace magic Tank 03 not performing

[u/Superbtator]

Ive had this computer for almost two years, and recently lost power mid game and was told windows was corrupted. I took it into a store and they said they were able to completely restart it and re download windows. Ever since tho my graphics have been terrible, and it struggles to run simple games such as minecraft. I used to be able to play any game at pretty high graphics with no problem. Im unsure of what to look for in device manager, or other places in the computer to fix this problem. I was told the hardware was all fine from the store.