First of all, the game screen is stuck on the left side of the PC screen. Also, I cannot move the game screen by touching the sides with the cursor. In other words, I cannot go where I want to. What happened?

Well, it'd help to know what game you're having this issue in.

Assuming you mean RCT1:
Don't maximize the game, just make it as big as possible with dragging the borders. That should make it not stick to the left side.
Also, to move around, either use the arrow keys on your keyboard or hold the right mouse button while moving around.

Thanks for your answer, but unfortunately it does not work. As soon as I expand the picture and try to drag it to the right, it gets small again. Also, arrow keys don't do a thing either.I don't understand it, because the game worked fine before.
BTW, it is RCT1.

I am not sure if you are having the same problem i had in rct but did you try holding right mouse button and moving it very fast to the right.

Is it the border left screen that simply jumps back when you go right?
Also you could try arrow up and left or down and right and see if you can move the screen.