How can i prefill questions from monday

i need to connect question A to board A
and connect question B to board B for a prefill

and than send the full form into board C with subitems.
is this possible?

Absolutely! Prefill logic is supported with our no-code API connectors: https://docs.feathery.io/platform/build-forms/logic/advanced/visual-rule-builder/no-code-api-connectors

do you have any example on how to connect the form with monday?

You could reference our API connector examples here: API Connectors - Feathery Docs

We don’t have a monday specific example, but we can help in a more white-glove way for enterprise prospects