Hi Manuel,
I am asumming that you want to amend or change users who already exist in Moodle, adding in fields like institution, department, city, country, lang, auth, timezone
In order to amend these fields you also need to add in the fields from the orignal upload so Moodle knows what accounts to amend namely
username, password, firstname, lastname, email
***Beware that you will be resetting users password back to the orignal upload.
Alternative
I you have PHPMyAdmin installed you can import the profile amendments only thru a CSV 'in file' (select the users table in PHPMyAdmin and then select Import) change the fields delimited by ; to , (CSV= Comma Seperated Values)