Heat pump efficiency at -12 degrees?

How good is the factor of how much energy you put into the heat pump and how much heating output comes out when it is -12 degrees?

I have a new air-to-air multisplit, SCOP 4.6.
The unit often freezes up, and from defrosting there is already a proper ice glacier under the device.
How much of the 4.6 is still left at -7 ... -12 degrees?

No idea, with my air-to-water heat pump the manual states a COP of 3.3 at -7. The lower it gets, the less it is. At -12 it will probably be closer to 2. But that’s just a guess.

I also think that it is 2 or even less, he had to defrost constantly. For now, the gas heating is running again (-9 degrees) until it reaches 0 degrees again.

Well, the efficiency can be easily understood if you have an additional intermediate meter and a heat meter for the heat pump. Thinking and guessing don't get you very far there. Especially since other data, like the flow temperature, are missing.

For -7, the question can be answered quite easily. BAFA has a large list of eligible heat pumps with their COP; maybe yours is included? Unfortunately, it only goes up to A-7/W35 (-7 degrees outside temperature, 35 degrees flow temperature). The good heat pumps come out in the range of 3.0-3.2, the majority are around 2.6, and some air conditioners even go down to 2.1. At -12, it's significantly worse again.

It does not matter what the coefficient of performance is at lower temperatures. Therefore, it is called the annual performance factor (Jahresarbeitszahl). In new buildings, it averages 4.5 if it is not messed up with a buffer or underfloor heating.

That the heat pump freezes once per hour and defrosts itself again is completely normal and says nothing about COP/annual performance factor.