Welcome to the Manjaro community @Gregor_van_Klomp
As a new forum user, you are encouraged to take some time to familiarise yourself with Forum requirements; in particular, the many ways to use the forum to your benefit:
The Update Announcements contain a Known Issues and Solutions section and should generally be checked before posting a request for support.
Output of the following command formatted according to forum requirements (see links above) is often useful (and this or similar will usually be asked for in Support threads):
inxi -zv8
This gives some (privacy-filtered) information about your system.
Regards.
Note: the first thing I would do is remove redshift from your system:
sudo pacman -R redshift
or
pamac remove redshift
as Plasma has its own, inbuilt day/night color adjustment tool. You can access it via:
System Settings → Colors & Themes → Night Light
