Very Slow App-Start if Wifi is on

[warmup]

I am desperate. I have had my MBP 16 for 6 months. So far everything has gone fine. even after the last update to 10.15.6 there were no problems.
A few days ago, without my being able to say what I was doing, programs started very slowly.
E.g. Chrome bounches the icon for 30 seconds before it opens.
The use of bartender is no longer possible because a click on the status bar takes 10 seconds ...

The interesting thing. As soon as I switch off the WLAN, the Mac runs completely normally and performs well.

I have already
- SRAM and NVRAM reset carried out.
- Signed me out of iCloud
- The combo update 10.15.6 installed again.
- Tried a new user
- No externe USB-Devices connected

I have no idea what else to do All the launch daemons look completely normal and unchanged.

Please help!! thank you

 

[warmup]

Okay here comes so solution after one day searching and testing :-(

It's right, that I haven't chance anything on my mbp.

After the second Mac at my home starts with the same problems the solution was mit pihole-server.
During the weekly scheduled adlist-update the apple-Site "ocsp.apple.com" was excluded ?
This seems to be a important site for the certification of software.
Horrible that a Mac is only usable without Wifi or with correct DNS-Server - without that software gets slow and also the build in keyboard and trackpad sometimes isn't known after waking up my map.