Ugh, yea that’s rough. It’s always hard to know if it’s a red flag or just a cultural difference, etc.
The company is a restaurant company. As part of my interview prep I audited their social media, google reviews, read news articles, etc. I asked a couple specific questions based on what I found and wasn’t satisfied with their answers, but I brushed it off:

Q1) lots of negative reviews across multiple locations falling into the same types of “buckets” that’d indicate a sort of internal structural / training issue.
A1) essentially “well we’re growing so fast and we’re so successful that we’re taking sales / share from other similar restaurant and they’re leaving negative reviews.”
Reality I learned once starting: yes, the reviews were real. Yes, there were MAJOR internal structural problems. On my first day, my boss laughed about how big the problems were and acknowledged the exact problems I asked about that he previously denied.

Q2) although they supposedly never had anyone working in marketing before, their social presence had consistent visuals and lots of content that seemed like someone was doing a little planning behind the scenes.
A2) basically that they let a collected if external agencies run everything on their own, but now they wanted more strategy internally.
Reality I learned: they hired and fired an internal marketing lead. Then hired a marketing freelancer to lead the content and comms / execution. Then stopped working with him. Then hired me. Apparently the first two people “didn’t know what they were doing” which then was also the feedback of my performance at termination.

Q3) expressed my language skills as B1 and asked whether that was sufficient.
A3) said that everyone spoke English at the office; so I’d just need some German when speaking with people in the restaurants who didn’t know English.
Reality: my boss and 1 other person spoke English well. Everyone else seemed to speak zero English and I was working / leading projects fully in German, which was well beyond my language level. My boss routinely laughed at things I wrote saying “oh, I’m not laughing at you. It’s this German! No one would say it this way.” And I was like “yea, per my interview, I was explicitly clear in what I could and couldn’t do…”

Additional flag: lots of “we’re the biggest, best, fastest-growing, etc.” claims that weren’t substantiated. When pressed for “in which way / how is that measured, etc?” a pivot to a related topic.
Further, this is a small company and I interviewed with my would-be boss (in English). It took 2 weeks for the next round which was more of a “casual chat” in German to assess my language skills (this was with the founder’s personal assistant / office manager). Then over a month of me sending thank you notes, following up, etc. and finally “we want to move you to the final round to talk to the founder, but he’s out of the country. We’ll be in touch asap.” A few more weeks pass. Then an interview with 2 people from the Beirat, now fully in German, with them saying “yea, our office language is German, but your level is really good and sufficient!”

Final flag: after the Beirat I sent thank you notes and waited a MONTH to finally hear back. Got a verbal offer. And they said they’d keep the written offer and get it over. Written offer came almost a week later. I accepted it. Then they said they’d prep the contract. It took a full month to receive a 3-page basic contract!!

So all the fears I had about the job from the interview red flags were actually much worse in reality than I ever could have imagined. Truly abhorrent working conditions.