I bought a bike, second hand, yesterday. The bike looks quite new and it is ok, but I notice that with some gear I got a clicking noise. After inspecting the bike, I notice that the chain does not flow steadely on the rear cassette, and this make the clicking noise. I don't know how to be more precise, so I uplodaded a video where the problem is quite clear:(second 5/6)
It seems to me that the chain is really close to the other disk (is it called cassette?), maybe because it is misaligned. Of course this is not only about the noise, I am afraid that it will ruin the chain/bike. Plus, if this is a serious problem, maybe I could just ask the guy I bought the bike from to take it back. However, I would be totally happy to solve the problem myself.
Please consider that I am a TOTAL beginner :) Thank you!