a few short basic questions

[yojoe]

Thank you for the answers

4) If the install directory is /getsimple/ does GS (installation or other) change anything outside?
e.g. the file ./index.html ?

Everything uploaded/added/managed/changed in your GS instance, stays in installation directory.
All data created by user or plugins are saved in /data/directories

9) For example the folder "Meetings". When clicking on it the folder openes and shows e.g. the file Meeting 26.04.2012 and other files.
So it is more clearly arranged.

Ahh you mean sorting under files tab ?
Unfortunately files are sorted only by type (directory/file), and name. Sorting by date isn't possible.

Another question:
Is editing and locking a page possible? (For any User)
So nobody can edit a page and nothing gets destroyed?

Fortunately somebody developed couple days ago such plugin.
I'd advise to go through whole extend, and see what plugins are available for GS.