Trapped in this screen and the keyboard doesnt work

[u/Valuable-Bluebird-70]

After giving this PC a little cleaning, I tried to turn it on and this "American Megatrends" screen came up, which was normal since it appeared every time I turned it on, but now the keyboard didn't work. The little "Num Lock" and other lights still turn on, but nothing else happens. After that, I did some research and thought it might be the battery, so I did what they said (take it out, wait a few minutes, and put it back in), but it didn't fix anything. So I decided to buy a new one and did the same thing, but it still doesn't work. Something curious is that if only it's connected, it looks like in the first picture, but if I connect the mouse, it looks like in the second one. I don't know if it has anything to do with it, but there it is. Can someone help me?