Drupal 8.x

I am new to Drupal and PHP. I am trying to modify the Hierarchical Taxonomy Menu module to display the current term's direct children, as I described in this issue. As part of this effort I have created this function within HierarchicalTaxonomyMenuBlock.php to get the tid of the current term's parent:

I was just installing some of the core modules (activity tracker, ban, big pipe, and one or two others), and the extend failed. I got a site busy message.

Now it fails at every page with:

The website encountered an unexpected error. Please try again later.

Nothing I can do seems to work. I’m not even sure where to start.

Any ideas? I tried going back in the browser and to many different pages with the same result on my Mac, and my iPhone. I’ll try a different browser but it appears to be the site. 

Hello

Is it possible to add fields from Group memberships to the User registration?  And also, is it possible to make any fields on the user page display only ie only editable by admins?

Hello, I am using this theme:

http://drupalthemes.us/medical/

and I'm getting a strange JS error:

Uncaught TypeError: Cannot read property 'date' of undefined
    at Object.attach (date.js:13)
    at Object.Drupal.attachBehaviors (drupal.js:25)
    at drupal.init.js:16
    at HTMLDocument.t (ready.min.js:4)

is this a known problem, is there an easy way to fix this?

thank you!

I am getting the following error message whneever I try to login to the admin area. Could anyone please help?

The website encountered an unexpected error. Please try again later.

I can not login at all.  I am using 8.4 Drupal version.

Thanks and regards