I know it's hard to answer without a video or picture...

Today I removed the brake pads to clean them (squeaky sound). After I replaced them, they are not symmetrical any more. Right pad almost touches the rim, left pad is a larger gap from the rim. When I brake, the left pad moves more (obviously) toward the rim. I tried to loosen the cable a little, but that makes the gap between rim and left pad too large. How to fix this? I'm afraid to unscrew anything that I don't know about to avoid messing up things, since brakes are so important for safety on the road.