Well.
Ill wait until tomorrow (as I cant imagine all zigbee devices stay in the network after changing the channel) and repair whats not working.
Then I know if I still am having issues or not.
Ill give message after.
Really no problem man! I think helping me isnt that easy, as I did understand many things here wrong. Making me a person you dont want to help.
But it maybe took a bit longer than needed - but finally we got it :o)
Thanks for continuing giving me advise! Really!
Sounds like something maybe went wrong with your Zigbee channel change as normally all your Zigbee Router devices should come back online within 10-15 minutes (because those are usually online so recieve the change command directly) and then after that you would normally need to manually re-pair all battery-powered and other Zigbee End-Devices.
You can try power-cycle each of your mains-powered to see if they automatically connect after that, if not then you are only left with the option to re-pair them (or restore the whole Zigbee network from backup).
Regardless, note that you should not ”remove” any devices, instead only re-pair them, meaning that you follow each devices manufacture’s procesure for pairing. You do not want to remove the device from ZHA because then it will get a new entity name and that means any automations using the old entities will need to be manually reconfigured to use the new entities.
Im gonna bet this ends up being the culprit. Just marking it down for posterity… Don’t go off path and Continue troubleshooting. You guys are on a good clip now. 
Nope.
The problems still exist.
I found out there is an issue already opened on gihub ZHA page.
As I never had such issues for 2 years and it came out of the sudden and there are lot of people having exactly the same issue than me, im thinking it really might be a ZHA issue.
Even more after excluding all the inteference stuff.
But as the uploaded logs in this issue look exactly the same as my logs do (amd I dont have any “working” logs), i cant provide any helpfullinformation there.
But I wanted to test z2m anyway - but never did because zha was working.
After changing the zigbee channel I would need to repair all my battery powered devices anyway. So Ill install z2m tomorrow.
Some of my devices are supported better there (with more entities, I would use if I had them). But as mentioned I didnt want to change the running zha.
Thats what im doing right now.