### Steps to reproduce

* Use a small screen height
* Click the 'Help' button in the top bar
* Scroll down

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End of the deletion ### Actual behavior

* Dropdowns are currently not scrollable themselves
* If a dropdown is longer than the viewport height, the whole website scrolls and this causes an additional scrollbar and an unpleasant gap at the bottom Begin of the insertion
* In the project menu the last entries cannot be seen on all screens. (For that the screen musst be small (e.g. turned mobile) and the list of projects should be long)End of the insertion

### Expected behavior

* A dropdown should have the viewport height as maximum and if longer should be scrollable within Begin of the insertion
* All project entries shall be visible.End of the insertion