Yes, the list will be imported with the edits you made in the sheet.
Mads, if you are trying to edit the name of the lead via a list import then that should work fine.
However if you are editing the "Lead OWNER first name" field, I don't believe this is going to work.
That field refers to a record on the user object (likely in SFDC?) and so I am *pretty sure* you can't just edit it via a list import. You would need to either change the user's name in the source system or do a re-assignment flow step to the leads in Marketo if that is what you are trying to achieve.
Hi Alok and Justin, thanks for your answers.
I guess I have to do manually in marketo or SF then