Was bedeutet I suppose not. ?

Sehen Sie eine Übersetzung

“Suppose” means:
- assume
- come to a conclusion
- decide based on a best guess

In your situation, it sounds like person B has come to her own conclusion about why person A doesn’t understand. She has figured this out not because of what person A said, but perhaps because of what she already knows about person A, or things that person A did not say.

For example, maybe this is what happened:

- person A is new to some situation, and person B is very experienced in that same situation

- person A does not yet have enough experience in the topic to realize why he doesn’t understand what person B is saying

- person B has finally realized this, perhaps after many conversations with person A

In addition, the phrase “I suppose not“ suggests that person B was trying very hard to communicate with person A, and is a little sad or disappointed: person A did not understand, and is not likely to understand anytime soon.

All that being said: Maybe anyone would agree all of that is actually true. But maybe that’s merely how person B perceives it, where person A might not see it that way at all. Or person B wants person A to think she sees it that way, to make person A feel bad. It’s a subtle situation.