Mirror Door Roller

I don't get it..maybe it's because my camera is a used camera.
when I look through the viewfinder, the mirror or whatever it is turns pitch black when I try to focus on an object 2feet from me. seems like I can only take shots ONLY in a well lit room or if it's sunny outside. I tried takin a shot lit by artificial light and it's sooo dark. even when the light/dark wheel is set in the middle. I don't get it!
on top of that, the camera has wear and tear that scares me.
at the front of the camer, just below the door and above the photo "slit" seems like it broke off and someone hot glued it back together. who knows how long that will last..
and the rollers...how do I clean them? I don't think my pictures are coming out of the camera fast enough...well compared to ppl on YouTube who have demonstrated their camera.