Hello,
1/ We are not able to add a product to the cart on your site. Please check product pages (shows 404 page) and your permalinks settings.
2/ “deactivated the theme” – does it means that you have checked the situation when default WooCommerce theme – Storefront is activated?
Provide us with a screenshot or video of the correct work.
You can use Lightshot screenshot or Gyazo tool to make screenshot and share the link here.
3/ Please provide temporary wp-admin and FTP access.
Create an account via Dashboard (Users > Add new) with administrator role http://prntscr.com/s3rc9m > provide us with username and password via the Private Content area http://prntscr.com/s5mao7 You can use any email for it.
If you do not know how to create FTP contact with your hosting provider, they will help you.
Regards