Hi there, @Clara12 ...
Sorry to hear that you are having issues viewing content in your Canvas environment. You might try clearing your history / cache files in your browser, closing the browser, and then restarting the browser to see if that helps at all.
How do I clear my browser cache on a Mac?
The only other suggestion I have for you would be to review the content in this posting:
What to do when Canvas looks 'big' or 'zoomed in'!
There may be other suggestions from other Community members, but this is what I suggest for now.
If these options do not work, I'd suggest reaching out to the folks at the Canvas Help Desk.
Please keep us posted here in the Community when you've found a solution...thanks!