First off, I'm a woman, so make it simple. Second, the water is overfilling. I opened the tank and after I flush it, it keeps filling until it overflows and then it starts draining through some tube, so I have to hit the flushing button or whatever you call it to release some of the water. How can I adjust the level of filling, or is there another way to fix this? Thanks :)

You can adjust the float ball that is on a metal rod. Bend it very gently downward and then carefully flush the toilet and see how far down the water is when it does stop running. If you've carefully bent it enough the float ball will shut the water off at the proper level.

This is either a malfunctioning fill vale or a poor fill level adjustment. Most fill valves no longer have a metal/brass float arm but newer ones have adjust meant screws. Which picture looks like your valve? https://www.askmehelpdesk.com/attachments/plumbing/12875d1224099054-toilet-noise-clip_image001.jpg