In addition, these tables in the database occupy much space, and it is impossible to make a backup:
Do I delete? or as I can delete unnecessary or temporary files?
There is a full migration guide here: https://forum.mailwizz.com/threads/migrating-mailwizz-to-a-new-server.10/ so try to follow it.
As for those database tables, if you want to have a smaller database, you have to delete some campaigns that you don't need anymore.
Please note that actual deletion happens at midnight, so you'll have to wait till next day or you can simply delete the campaigns you don't need from phpmyadmin.