This seems to be two problems:
This is familiar to what users are reporting here:
https://forum.fairphone.com/t/google-sync-lost-after-update/9720?u=9x6
I’ve posted my own experiences in this thread as well. For me the steps I provided there fixed having to manually retrieve mail. Clearing the cache of google play services is a good chance to get back play store functionality as well.
Now the wifi completely not working is another thing. I can’t see the picture you referred to, but I’m assuming you’ve seen this post and the problem is similar (if not, what do you see?), as you mention:
So, which one did you find? It should be at the position mentioned on XDA (/data/misc/wifi/wpa_supplicant.conf), though you can only access this file as root or via apps that use root. Note that removing this file will wipe your saved wifi settings. Just out of interest, do you use F-droid? (If you’ve never heard of it, you probably don’t) - so far the only issues reported to be fixed by removing this file were caused by F-droid.