Hi @DanijelJuric -
Based on the image you shared, it looks like you've met your file storage quota. While you are unable to increase the space you have available, your local Canvas Support team should be able to help you.
I see you're from Penn State! I was able to find this information on their website: For help with Canvas, contact firstname.lastname@example.org. Faculty and staff may also call 833-846-7691, and students can call 877-226-4449.