My new laptop is messed up?

Well I just bought a new lenovo ideapad 500S costing 1.4 sg dollars and it is really making me frustrated. I believe it has a graphic card and intel core 7 so I should be able to play league of legends. Furthermore the salesperson said I could so I kinda trusted him. But ever since I downloaded the game, which was the same day as I bought it, the laptop hanged while loading to start the game. Then it hanged again the second day while I was on fb. It has also clicking noises from time to time, and lastly while watching youtube videos it pixelates and lags after scrolling through the comments, but the audio is still working fine. I know I should have tried to exchange the laptop or something the first 5 days after I bought it but I was busy going for e orientation camp. Now I feel like it is either lol ruining my laptop or the laptop itself that is already ruined. I really want to play lol though, but It is very important for school because lessons evolve around my laptop. What should I do?