Have a good result with QnA

I recently got interested in botpress to see what it can do.
After having encountered some difficulties to install it with a dedicated language engine and understand some subtlety of the flow (thanks to the forum for the help available!), I now appreciate features of botpress.
However, like some recent posts, I do not get good results with QnA.
For test, I have indicated some questions with some utterances in 1 context.
I append this context in a node after a choice node then, when I typing a dialogue with a single letter for example, the NLU links to one of these questions.
I expected there to be no correspondence : NLU -> none match.

How to arrive at a correct result with QnA? With what flow for use context ?

I think I will have a lot more questions … :sweat_smile:

Thank you for your answers !