Since OP clarified that he does indeed consider himself very good at interviewing, I'll expand on that point a bit: Interviewing well is a useful skill and there's nothing wrong with that per se. The problem occurs when you promise things you cannot deliver. So there's two ways to approach this:
- Manage expectations by emphasizing the ramping up stage. Your position should be "I'll be really productive, but not for the first 1-2+ months". If you simply ask a lot of questions about onboarding and how they handle setbacks this already implies, whether intended or not, that you anticipate a non-trivial learning curve when you start. If you are running into problems with unfamiliar technologies, you can also point out that you don't have much experience with parts of their tech stack - of course you probably want to show at least some familiarity to be hired at all, but you don't have to say you know every single piece of software they use (and then be expected to use it immediately).
- Take the same dedication with which you studied for interviews, and apply it to basic job survival skills in your domain. It should go without saying that, at least for the first few months, you should always do everything your boss says. If you are unable to finish a task, make sure you have put an appropriate amount of effort into it, and be able to clearly explain to your boss how far you've gotten and where you got stuck. Understand what the day-to-day is like for jobs you're applying to, and make sure you have at least some basic ability to navigate that. For example, a job where using git is bread and butter, you want to learn as much git as you can before starting if you claimed that you know it in the interview (and you shouldn't really claim to know things if you don't).