Restaurant/bar rec’s for a celebration

I’m planning a small celebration and will have 10-15 people present. I’m looking to hold the celebration in a restaurant or bar. It will be the weekend of the Berlin marathon, so a pretty busy time in the city and I’d like to plan early.

Can you recommend any bars or restaurants that:

- Accept reservations pretty far in advance
- Are good for groups and not too loud for talking (maybe offering a private room even)
- Don’t have strict limits on how long we stay for (ideally no “reservation valid for 1.5 hours” as some might not be able to join at the start)
- Are centrally located ideally, but at a minimum are within the ring
- Have a nice vibe without being very expensive €€€

An example: A friend hosted his birthday at Minimal Bar in Fhain a few years back. He was able to reserve a room for free for the night and it held about 15 of us. I don’t want to repeat the same location, but that’s the kind of setup I’m looking for.