How to import text to columns and import numbers to text in macOS Numbers?
Not sure which version of Numbers you are using but one can adjust import settings from a text file in both Numbers v6.1 and v10.2 and it works resonably well in my experience.
Just open the text file using Numbers and a popup menu will emerge saying &quot;Table data was imported. Adjust Settings&quot; as soon as the file is opened. This menu disappears after a few seconds but you can adjust the same settings using an option in the sidebar menu as well as described in this Apple support page.
As for your second question, sorry that I don't know in general how.