It's a single core game.

That means, graphic cards and settings are pretty much irrelevant. All that counts is the speed a single core of your multicore cpu can deliver.

It's easy to test: change to minimal graphics settings, the game will use less RAM for the whole game than most modern GPUs have. The speed problem won't go away, though.

Then run task manager and watch: one core is constantly maxed out, even if the game is paused (!!!) but the other cores are idle.

With any good GPU it's even possible to run other games on the second screen without any further slowdown.

I'm horrified by the inability of the developers to fix this problem. Yes, it's not always easy to use multithreading, but especially planning for multiple AIs means: every AI could use a single thread. Somehow, they did create the game in a way that it seems too difficult for them to do such a change. Very strange. Maybe they should hire specialists who can in order to deliver the multicore support that is advertised.

Since you're german: You can return the game to the store according to german laws. Not entirely whats desired since you cannot play the game any longer, but it may help to put enough pressure on the developers to fix this.

Screet