You can upload large archives to unzip/unrar them, or create large archives to download them; large files are allowed a four-hour (approximate, could be slightly longer) lifetime. Files that are going to remain need to be kept under 10MB. There is no "daily limit", but if you haven't yet been granted unmetered space¹ or if the actual shared data drive is full (which will return a 521 error)², you may not be able to upload.
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¹ All new accounts have limited space to begin with, usually 512MB. This is to prevent "drive by" abuse, which you get a lot of on a free service that requires no more than a valid email address. Once your account is more than 7 days old, is fully within the Terms of Service, and is using more than 50% of your allotment, you can request unlimited space here.
² When the disk is full, the disk is full. In order to prevent file corruption, all disk writes are prevented until the issue is resolved. Staff will either have to free up some space or provision more. That can take a few minutes or a few hours (longer if hardware needs to be provisioned or if there is something doing a lot of writing to disk, filling it up as fast as things can be deleted.