Hi,
The issue comes from the user groups.
Under the "Access level" tabs of the HikaShop configuration, HikaShop will add a checkbox for each mode of each data for each user group.
So with around 20 views and 3 modes for each and 3000 user groups, that's 180 000 chekboxes displayed and then processed during the saving. That's a hell of a lot for only one page.
Edit the file config / config via the menu Display>Views for your backend template and remove the line:
$configTabs['config_acl'] = array('ACCESS_LEVEL', 'acl');
it will remove the "acces level" tab from the HikaShop configuration and you should find a fast HikaShop configuration page again.