Good luck!
Wow - really helpful input here within some hours. Thank you so much - seems to be a great helpful forum here.
It's very difficult to discribe my problems in english, so I hope I don't forget something. In fact one of my worries is, that my steerer tube is a litte bit to long an so the top-cap doesn't work right. I will post a picture later.
I did a lot of research and try and error with a compression plug and it finally endet with a very long (and heavy one) - my favourite Specialized Plug won't work because it lies on the steerer tube and then I don't have enough space for the cap (same level plug and stem).
In fact it feels like the first few miles are ok and then something feels loose (in fact nothing is lose) - so my guess was, that the half-compression ring has to much clearance or something like that. If I pull my frontbreak and move the rest of the bike (by holding the frame) I feel the movement and a little cracking sound.
I didn't come to a ride so far, but my first thought was to use another spacer to get the stem higher --> top cap problem, so I will try this.
Unfortunally they send me the one bolt bar/stem and say that I have to buy the 2 bolt for XX€.
As you can see I am very upset with the whole front-end and don't now why: bar/stem, headset, compression ring...