Guidos

No problem at all, thanks for confirming that for me and your screenshot provided!
There have been many fixes and improvements implemented into V2, which certainly might benefit your workflow - especially for the newer 'M' based devices from Apple.
You can try a free 30 day trial of V2 from the below link, to see how this impacts your machine:

https://store.serif.com/get/universal-licence-2/trial/
Please note that Affinity documents are not backwards compatible from V2 to V1, so please ensure you are working on a copy of any V1 files in V2.
 
In regards to your V1 screenshot, I'd recommend unticking Hardware Acceleration at the bottom of this dialog, then changing the Display from Metal to OpenGL. Now restart the app as prompted and try editing your document once again - hopefully this will reduce the freezing behaviour for you

If it freezes regulary afterwards it could be hardware acceleration related as Dan C already suggested to test out. Or some font caching issues.
It always depends on what operations is performed here on/with the text and also how things are internally implemented here then for the used objects memory allocation & deallocation. Meaning it's not everywhere (in all different apps) handled the same way.

Thanks for the further information provided @Guidos, can you please navigate to Affinity Photo > Preferences > Performance and provide a screenshot of your settings here for me?
Have you tested the V2 trial on your machine, or is this based on similar reports you've seen here for V2?
If you have tried the trial, is this a recent version (ie 2.1 or later) or was this previously tested, when we first announced V2?
Many thanks in advance