There is no such thing as a stupid question: Each question is a genuine request to become more informed about the world.
If there's a metric to measure your onboarding, it's the amount of questions you ask.
Don't worry about how you'll look when you ask a question. If you have taken the time to choose a healthy team, they will not think any less of you for asking.
It's much better to ask questions than to be stuck for days, if not weeks. If you're completely stuck after 15-30 minutes, just ask the question.
If you're asking questions in a public forum (which you should!), you are creating content with your Q&A pair. Not only are you benefiting by getting unblocked, you are having multiplicative impact by creating a useful resource that will help the team across the future.
If you are asking questions the right way, people will not get mad at you for asking questions.