The following happened: Yesterday on the highway I noticed that the engine somehow does not run as usual. Stopped in the next parking lot and.......it only runs on 7 pots

Half the night I didn't sleep and set up a horror scenario that could be anything.
Panisch then I am in my distress at eight this morning as a friendly person and I described the situation and left him with a tear in my eye.
At 4 p.m. I received the expected call from the workshop (between 16 cups of coffee and over 40 cigarettes), starting with: "...Are you sitting???? "
Cylinder 4 has 0 compression

Cylinder 1: 12.0 2: 11.1 3: 9.6 4: 0.0 5: 12.1 6: 11.4 7: 11.1
8 has 12.1
You can also hear when he runs a hissing like if a spark plug would be loose !!!!
Should I put another head on it ??? Should I replace the valves which are defective ????
What do you think is the best solution and who can possibly help me without having to crash my account into the deepest abysses?

I have never been so perplexed and hope for help !!!!
"Thickness" Greetings from Saarbrücken
Jürgen

