When I try to change my profile picture its says the max. file size and the max. image size, but I don't know how to make the image file size any lower because I'm on a chrome book with a lot of school restrictions. I need help!

You can use ezgif's resizer to resize it to 500x500 or below.

Anyways your pfp will get resized in the forums.

Correct me if i'm wrong but I think the lower resolution the lower the file size.

I would suggest importing your image into a project, and then using ctrl + shift + f5 (the selective screenshot shortcut on chromebooks) or generally just right click - export if you have no idea how to use selective screenshotting.

Once you do this, you will have one bootyful PFP, scratch-ready.