“I don’t know yet, but I’ll find out” might be the most trusted sentence at any new job.

Admitting a gap and committing to close it signals two things at once: that your answers can be relied on, and that you will handle what you do not know without supervision. Guessing gets you through the conversation and costs you the next one, because people eventually work out which of your answers were invented.

Use the honest version the next time you are asked something outside what you know. Then actually find out, and come back with it unprompted. The returning is the part that builds the trust.