Drupal 8.x

We upgraded our multisite instance from drupal 8.5.1 to 8.5.2 last night and one of our sites is now unavailable.

I'm really not sure how to do this.  Basically, if a user is a member of a Group (using the Group module) I need them to have up to 4 dependant fields in their profile (in this case, priority one, priority two, priority three, priority four).  These fields are only relevant if the user is a member of a Group, and a user can be a member of more than one group.  Any ideas?

[for Drupal 8]

Hello,
I submit to you a general problem that I have been trying to solve for a while. A classic case that I know how to solve in terms of database but I do not find a simple equivalent in Drupal:

I have :

I'm crazy with Drupal 8. I made a form and I do not know how to make it visible on my website, I do not understand how it is done. Now that I have upgraded to 8.5.1

I can not access anything from the administrator. Here's what it shows: "The website encountered an unexpected error. Please try again later"

Every time I update from composer, the accesses are damaged. (composer update)

What I do...?

Regards

I've created a simple custom fieldtype called measurement_range. Everything seems to have gone correctly, per a few tutorials I've found online. I enabled it, there are no errors seen (devel is turned on) went to add a new field to my content type... but measurement range isn't there. Not sure what to do now. Tutorials don't cover this. 

in case it's a problem, here's my file structure: 

Hey guys,

I'm kind of new to Drupal 8 development and object-oriented PHP in general. I've been trying to make a simple custom block module, which includes a service with simple dependency injection. However, I can't seem to figure out why the construct method does not receive an appropriate parameter - been staring at the code for hours. My code:

event_countdown.services.yml