Update to 3.6.5 Joomla via backend

Hi Guys,

Just thought I would update to a later version of Joomla.
Now, once you edit any modules it just comes up with a picture of the position field (and nothing else on the page)
I then went in and updated php to 5.6 and is doing the same thing (as I think it used to be 5.2).
I then went and changed the php version to 7.1 and then after tapping on one of the modules, it returns the following:

This page isn’t working
www.liddleones.com is currently unable to handle this request.
HTTP ERROR 500

The front end is still working fine, but I need to go and change a few articles and can't do it.

The "Minimum Requirements" link on your page for Creativity doesn't work, so am trying to find out what the problem is?
can you please advise what the problem might be.

Website is http://www.liddleones.com/

can post passwords if not an easy fix in the forum.

Thanks.

Also, if I change the php version to 5.4, it returns the following:

"Error displaying the error page: Application Instantiation Error: The MySQL adapter mysqli is not available"

Could you please provide me with a URL to your website back-end and FTP access via PM (click the “Private Message” text underneath my avatar) so that I may analyze it?