I am using Interactive Brokers and Trade Republic for this one. Worked fine with IBKR; with Trade Republic, I had to file another acceptance instruction after the offer price increase. A colleague of mine did it through Deutsche Bank maxblue, and it was also sufficient to file the acceptance instruction only once.
As settlement is generally T+2 in Germany, it should theoretically work until Wednesday, July 1. Usually, brokers have shorter acceptance periods, but you can sometimes extend those by contacting their customer service.
I can generally recommend IBKR, as they seem to be the fastest when it comes to notifying you about the offer.