it's often not possible to save
I tried overwriting a save, and to save a new one, I press yes, but nothing happens
Unfortunatly it really doesn't save so I had to play scnenes again and again...

how to solve this?

Ensure you install the game and run it as administrator.

Running as admin does not solve the issue.

For anyone having issues with not being able to save the game, use a large address aware application on the game.exe file (you will have to point it to that file yourself).
I have noticed that the developer has offered up NO solution whatsoever which is very poor.
This does fix the issue but shame that a customer had to work out the issue themselves.
To save you from looking, here you go (make sure to tick the box) 'large address aware flag' and save:
https://www.techpowerup.com/forums/threads/large-address-aware.112556/

This has worked perfectly to fix the save game bug, thanks a lot Bulldog_UK!