SUMMARY

Deleting some time intervall completely from the timeline should update the position of all markers and keyframes AFTER the deleted part, and (possibly), and delete all markers IN the deleted time, and usefully update OR delete all keyframes IN the deleted time.
Currently it does NOT change them. So keyframes and 

Besides, the naming of the German and English menu entries for these timeline functions are not optimal (other functions not yet reviewed).

STEPS TO REPRODUCE

1. Have any project with markers and/or keyframes
2. Select some time interval in the timeline. Then chose:
English: Timeline - Removal - Extract timeline zone
German: Zeitleiste - Entfernen - Zeitleistenbereich extrahieren


OBSERVED RESULT

The audio and video elements IN the selected "timeline zone" are removed. This is ok.
All audio and video elements AFTER the selected "timeline zone" are shifted left by the time equivalent to the duration of removed time interval. This is ok.

I do not know what happens to markers and keyframes IN the selected "timeline zone".

The markers and keyframes AFTER the removed timeline zone, however, remain completely unchanged.
So afterwards, these markers mark wrong and meaningless positions.
And the keyframes cause effect changes at wrong and meaningless positions.

EXPECTED RESULT
All markers AND keyframes AFTER the removed "timeline zone" should be shifted left by the time equivalent of the duration of the removed time interval. (This is the bare minimum :-)  )

All markers IN the removed timeline zone should probably be deleted. (This might already happen.)

The first and the last keyframe of any given effect IN the removed "timeline zone" should most probably be replaced by two keyframes at the last frame before the excision, and at the first frame after the excision (these two should be neighbouring frames); probably with interpolated values for keyframe data that would have applied to the same positions BEFORE the excision of a time zone was performed.
OR - they might just as well be merely deleted (less graceful...), so that any interpolation across the deleted time might remain seamlessly intact.
OR - a dialog or a further submenu should offer various options.

SOFTWARE/OS VERSIONS
All versions are probably affected.

ADDITIONAL INFORMATION
The naming of the menu items do NOT optimal in both German and English.

I'd suggest the following changes (to make it clear that one option removes time, and the other removes content):

English:
Timeline Zone -> Time interval
Extract Timeline Zone -> Remove time interval from the timeline
Lift Timeline Zone -> Free time interval from content

German:
Zeitleistenbereich -> Zeitintervall
Zeitleistenbereich extrahieren -> Zeitintervall aus der Zeitleiste löschen
Zeitleistenbereich herausheben -> Inhalte im Zeitintervall entfernen

The best choice between "Remove, Cut, Delete" may depend on whether the removed portion actually goes to the clipboard, or just vanishes.