[kaiser]

I think you have a leak. I have just had one on my two metal pipes and on the main cooling pipe from the thermostat. I also did a sniff test and it also changed colour, eventually.
If you let your car idle, the water level will rise, if you wait long enough, it proves nothing in itself.
The leak can be difficult to find.
Get the car on a lift and inspect. Don't forget the water pump, which often can show up as a trace of water near the pulley!
Get the proper cap from BMW, don't worry about the 200 printed.

A compression test is not a good test for the head gasket. Pour a bit of oil in the bore. Repeat the test. If improved - rings, if not - valve.

If you continue to look for signs of hgf, everything can be taken as such, but essentially you are looking for a leak.
Also make sure your fan works! and monitor the temperature, if you can on your instruments.

If you look, you will find it.

The copy below is what I recently experienced on my engine.

I know the V6 engine well, and yet, recently it fooled me.
My daughter used the car everyday for an extended period, and came home one day with the fan running.
I felt the pipe to the radiator being cold and assumed a stuck stat. Since I make them, I was not overly concerned by having to replace it, as this car still runs with the prototype I built nearly 9 years ago. So I ripped it out and tested it. It is made from steel pipes I machined and welded together, so it was rusty, but in spite of the bad looks, it worked! Which surprised me.
Anyway fitted all, and the engine would not run properly. Turned out I could not get the inlet manifold down far enough, because the rear plugs for the injectors faced towards the back, and were then high enough to prevent the manifold from coming over the green O-rings! Sounds easy enough, but it had me stumped on more than one occasion.!
Anyway, getting the engine to run properly, then showed that it would still overheat, and it lost water.
I thought the head gasket was gone, but after a searching I found two pinprick sized holes in the two metal pipes under the radiator, both on the corners, and one in the main rubber pipe from radiator to thermostat. Both were low and facing to the back, and in retrospect must have let out water while driving in a spray that was not easily noticeable, by the time you stop to check, no leak because the water had already gone!.
I am happy to say that the car is now fixed, but it required a repair of the bleed screw in the pipe as well, as that has had it, (another piece of plastic!) and the bypassing of the oil cooler, now done with a bend pipe to retain the original hoses for the cooling system.
So the moral of the story is find the water loss!

Also, in addition, when I ran the engine in the workshop, I had water coming out the exhaust, and condensing on the concrete floor. And quite a bit of it, I thought. That added to my suspicion of HGF. When you get into this mind set, you see everything in the light of HGF. It is of course possible that you do have a failed gasket, but be very careful of cementing your views, they can easily lead you astray.