Plug In Testing For WordPress Website

We updated our website to wordpress 5.1.1 however this has impacted some of the old plug-ins which means they no longer function. It also means that we are unable to edit the pages. We would like some help in testing and updating the plug-ins. We would like and expert with wordpress plug ins - these have never been updated since the website was created five years ago.

Previous history:

The original version of wordpress was 4.8 and it was updated to 5.0 last year. No plug-ins were updated during this update however the website functioned normally.

Kind regards