If I sell for other people in my webshop, how do I get a list of what every seller/affiliate have sold? Can't find it anywhere. Tried to add the customized column "affiliate_id" to the order export file, but it did not work!

"affiliate_id" isn't a default parameter.
 
You would need to edit /admin/admin_table_orders.php
 
Find
 
"affiliate_code" => array("AFFILIATE_CODE_FIELD", TEXT, 4, false, ''),
 
And add after
 
"affiliate_id" => array("Affiliate ID", INTEGER, 2, false),
 
This will then show when you export sales /orders as an option that you will need to check.