Ist alles okay mit den Weintrauben und kann ich die noch verzehren?

I think this is a sort-related coloring.
The stains are part of the fruit color. Unobjectionable.

More headbreaks in grapes in general, I do about possible plant protection residues. Wine grapes in the farm garden are very easy to maintain. And this is not regulated as strictly in many countries as in Germany.

If you have concerns, you can try two, three berries and wait for what happens in the next few hours.
Grapes (here table grapes, if it is a sweet fresh-food variety) are like fresh plums or cherries: You can’t eat too much at once anyway.