Phone calls with the new Phone 2026

Soooo, I intalled “CellMon” from storeman.
At home my signal strength is horrible:
(4g only, everywhere, even if I 100% know 5G is available.)
Status RSSI 1%;
Cell RSSI 10% - 16%.
The indicator at the top right corner has one bar. (I guess out of 5.)
I was driving around now in the car and making occasional stops.

The very best I had was
Status RSSI 52%;
Cell RSSI 65%. (3 out of 5 bars in the top right corner indicator).
Ironically this was at the spot where I needed to make the emergency call on Tuesday.

My father came with me and and checked in parallel with his 4G only android phone.
His results are not comparable 1:1, but it was mostly better. At least the singal strength indicator showed often 5 out of 5 bars. The signal strength measuring app was not always making sense.

Until now I never saw my signal strength indicator at the top right corner full, best was 3/5.

Why is the phone not connecting to 5g, even if available?
(I saw this one: Jolla Phone does not support 5G for several providers in several countries)
Is this because of the setting “4G phone (VolTE)” registration?

thanks!