Hello Sherry,
Backup shouldn't take long unless you include massive submission data. We've tested with 25,000 submission records and took us ~2min max with PHP 8, Nginx, MySQL. If it takes longer than that, something is not right. 

Can you explain more about the sample forms that are not loading.
- Were you prompted with an error message? Or was it just blank?
- Does your Joomla! has the read/write permission on the tmp folder?
- Can you check if the tmp folder path configured in the Joomla! global setting is correct