Köster is okay, we almost chose it too. The top priority was that the door has a Fuhr lock, which already ruled out most options. The second priority was that it should be a door that no one else has. I just hate those standard doors you see in 95% of new buildings. In the end, we chose a Securidoor wooden front door. It has a scratch-resistant panel coating (HPL 4 mm) and surely nobody else has such a door. But it was also expensive. Otherwise, we would have taken the Köster door, so I'm giving a recommendation for it now. Those were both-sided wing-overlapping and triple glazed and priced exactly at the same level as the Securidoor door (6000 with side panel). Ultimately, it’s like everywhere: if you want to pay as little as possible, you get corresponding quality. At 2000 euros for a front door, regardless of the brand, you shouldn’t be surprised, for example, with aluminum, if the door warps and doesn’t close properly (metal and temperature fluctuations...). That’s why we ultimately chose a wooden door. By the way, you can also find cheap doors at 1001 Tür inklusive Fundgrube, where you can get returns very cheaply if you are still flexible with the measurements. They also have the bigger names in their program.