Prestashop backend crash... after changing from catalog

[SPES]

Prestashop backend crash...

New user/merchant and still setting up shop Learning. https://spes.co.za/eshop/

After having spent a week making up products, pages etc I still could not get to order on shop... pages came up and could go to products. but there was no link/action button to make it a 'shop'.

After online search found a topic that said must change a page setting for to catalog to off: Done this and saved, whole backend crashed and just comes up with this message:

Quote

Oops! An Error Occurred
The server returned a "500 Internal Server Error".
Something is broken. Please let us know what you were doing when this error occurred. We will fix it as soon as possible. Sorry for any inconvenience caused.

Well Good news is can enter shop and place order... bad news there is errors on [like not including shipping cost!] and cannot even bring down for maintenance. This is urgent, please help