Hello yehuna / Joachim,
welcome to the Ca3DE forums, and many thanks for pointing out some important problems with the documentation!
About your question about static detail models:
There is no need to modify the
fgd file - just place a point entity of type
static_detail_model as described at
http://www.ca3d-engine.de/wiki/doku.php ... :newentity somewhere into the map, then make sure it is selected, and bring up its "Properties" window (Alt+Return, or via the menu).
In the Properties window, select the "Model file name" property from the list and set its value to the desired model name, e.g. "Models/Static/television.ase". You can use the "..." button near the "Value" field to select the desired model, as it will also help you to get the path right (namely relative to the DeathMatch/ directory).
The model will be loaded as soon as you select another property with the mouse or close the Properties window.
If this was a too short description, please let me know, I'll elaborate then.
You're also right in pointing out that this is currently missing from the documentation.
I'd be very happy if you wrote about this in greater detail in the wiki.
Personally, I would suggest to add a new section "Placing Static Detail Models" at the end of
http://www.ca3d-engine.de/wiki/doku.php ... :newentity
(instead of filling in the currently missing "Placing a model" page in the Tutorials section).
About your question about the sky domes:
Thanks to the MatSys, making a sky somewhere just requires to assign the proper material to the desired surface, either immediately when creating the brush, or later with the "Edit Face Properties" tool. You've probably found out so much, too.

Again, the Tutorials section mentions a still missing page "Adding a sky", but as before, I'd suggest to instead write this as a separate section either into the documentation of the
NewBrush or
EditFaceProps tool -- which however are both still missing, too.
Joachim, I'd be very happy if you'd help out with writing documentation. There is no need for a translation into German [I prefer to keep things international

], but there is a big need for filling-in missing things, as you've already discovered.
Please let me know whenever you need help -- I'm happy to assist, as I'm happy that you like Ca3DE.
Please also see the resources mentioned at
http://www.ca3d-engine.de/phpBB2/viewto ... =2017#2017 which I have uploaded to assist with writing the missing documentation.