okay the language files you can edit to satisfy you
Have you uploaded all the required templates and php files? Your install is acting like an old bug that was like fixed in 2.4
Make sure uploadproduct.php and uploadproduct templates are uploaded as in the php file there is this
if ( $process != "do" ) {
then in all the templates there is this
<input type="hidden" name="process" value="do" />
WITHOUT THIS STATEMENT IN THE TEMPLATES YOU WILL LOOP AND NOT ALLOW UPLOADS
I still had admin access on your install and looked at your templates and indeed you have old templates there and not the new ones