I've had to jump into projects with unfamiliar setups and even unfamiliar languages more than a few times, and after a certain point it's all just problem solving. Like I had to fix critical bugs in an orphan rails project with next to no experience with Ruby and it worked somehow.
Are you going to write elegant, idiomatic code in the first week? Of course not. But give the task "make the system do X", 90% of coding is knowing how computers work, and the other 10% is knowing how to search on stack overflow to be able to translate what you want to do into the desired syntax.
Are you going to write elegant, idiomatic code in the first week? Of course not. But give the task "make the system do X", 90% of coding is knowing how computers work, and the other 10% is knowing how to search on stack overflow to be able to translate what you want to do into the desired syntax.