Hi thanks for the suggestions. I found late in the night a hint in galciv3 FAQ about a similar situation and the suggested solutions was "Error: Could not create your Galactic Civilizations Ill user data folder.
On Windows 10, go to your 'Windows Defender Settings' --> 'Virus and threat protection --> Ransomware protection --> Turn off 'Controlled folder access'.
This worked for me, the game loads now without problems.
