"not really" and "really not"

[ref1]

1. If the teach asks "Do you understand?"
And then I answer: "Not really!". Does it mean I answer "I don't understand at all" or it means "I understand a little bit, but not sure" ?
2. If I say "I really don't know" and "I don't really know"
Are they different? I think "I really don't know" means "I don't know at all - I don't know anything about it" and "I don't really know" means "I know a little bit about it"
Am I right?
Thank you!

[5jj]

1. If the teacher asks "Do you understand?"
And then I answer: "Not really!". Does it mean I answer "I don't understand at all" or it means "I understand a little bit, but not sure" ?
The word themselves suggest your second interepretation, but many people use them when they don't understand at all. They do this for a variety of reasons. When saying this to a teacher, they may just wish to avoid appearing stupid.
2. If I say "I really don't know" and "I don't really know"
Are they different? I think "I really don't know" means "I don't know at all - I don't know anything about it" Yes
and "I don't really know" means "I know a little bit about it" Possibly. See my answer to #1.

5

[TheParser]

1.
2. If I say "I really don't know" and "I don't really know"
Are they different? I think "I really don't know" means "I don't know at all - I don't know anything about it" and "I don't really know" means "I know a little bit about it"
Am I right?
Thank you!

CAUTION: NOT A TEACHER


(1) "Really" is my favorite word, so may I add my two cents?

(2) Really, I do not know./ I do not know, really.

(a) I believe that in those two sentences, it means something like:

Believe me/ In reality/ In fact/ I am telling you the truth: I do not know.

(3) In "I really do not know," I believe that it has the same meaning, especially

if you stress (pronounce strongly) the "really."

Tom: Do you speak French?
Mona: No.
Tom: You lived there for a year. I think that you do speak French.
Mona: Believe me! I really don't speak French.
Tom: How can that be?
Mona: Well, I associated only with English-speaking people. I saw no need to learn French. I felt it was the responsibility of the French people I met to speak English. I am very proud that I speak only English.

(4) And I agree with you regarding "I do not really know." That is, I know a little bit, but ....

Martha: How long were you in Beijing?
Ralph: About 6 months.
Martha: I bet you learned how to speak Chinese.
Ralph: No, I didn't.
Martha: Don't be modest.
Ralph: Oh, sure, I learned how to say "How are you?" and "Thank you" and "Where is the restroom?" but, believe me, I do not really know how to speak Chinese.