hi
i have issues with loading one of my database in dashboard after filling it with 1500 line
and its seems as a big failure in WIX system because one night before it was ok , and since that time nothing change in my website
You would be better suited contacting Wix Support for that issue.
https://support.wix.com/en/about-wix/contacting-wix-support
Plus, have you tried checking your internet connection and simply closing browser used and deleting all cache and cookies for it.
You can have unlimited rows, however you can only upload 1000 at a time.
https://www.wix.com/corvid/forum/community-discussion/collection-data-limit