Zvoni, ... I cannot understand, what you mean, although we both speak German.
Let me start with translating:
The error message of the screenshot says:
".... could not be opened. The file may be damaged or permissions not granted."
The checkbox checked says "allow to run the file as program", group "sudo".
All permissions are set to "read and write".
Then I tried the terminal line suggested by Bannon and read:
"The package list or the status file could not be read or opened."
A deb-file is not an executable. So setting it to "allow to run file as program" is nonsense.
A deb-file is more similiar to a zip-file
"GDebi" is a little tool available on Ubuntu (and derivates, which Mint is).
From command-line: "sudo apt-get install gdebi".
I used that to install deb-packages when i was still on Ubuntu.
Start GDebi (it's a GUI-program with a Window), select your deb-file and off you go.
Well, and the deb-file actually being completely downloaded (File-Size of deb-file?) not withstanding......
EDIT: Wait a second.
Your Linux is in a VM (VirtualBox?).
Did you download the deb-file WITHIN the VM or outside (on your Windows-Host)?
If it's VirtualBox i think to remember, that the Extensions have to be installed (and the option be activated) to be able to move files between Host and Guest