Create two entities, let say import with import lines. Set the reference so that one import has multiple import lines. Now do an excel import on the import lines, but also set the reference to the import object. Your result will be after the excel import that you now have one import object and a lot of import lines with the actual data of the excel document.
Now you can do all kind of things. From the import object you can see which user created the import. From the creation date of this object you can see when this has been done. The number of lines can be retrieved by a microflow that retrieves all the import lines with a reference to the import entity.
I never import directly to the object I want to have the data in. I always do the import on this shadow entity and then process the data after the import. This way you can elaborate your log with all kinds of info when you process the data. So you could create a new entity logErrors with also a reference to the import object. Each time when you process a line and you have an error create a new error log with the text message. This way the user can have detailed information about what goes wrong during the import.