1. I totally disagree with you.

2. I completely disagree with you.
3. I entirely disagree with you.
( Do they mean that I don't agree with you at all?)

4. I totally don't agree with you.
5. I completely don't agree with you.
6. I entirely don't agree with you.
(Are they grammatical? What is the difference in meaning? partial negation?)

You're right about 1, 2, and 3.

For 4, 5, and 6, the ideas are correct, but the phrasing is a bit awkward. Better would be any of these:

I don't agree with you at all.
I don't agree with you.

1. "I totally disagree with you."

2. "I completely disagree with you."
3. "I entirely disagree with you."
These three sentences all convey the same meaning which is that you do not agree with the other person at all. The words "totally," "completely," and "entirely" are all adverbs that emphasize the extent of your disagreement. So, all three sentences indicate a complete lack of agreement with the other person's viewpoint.

4. "I totally don't agree with you."
5. "I completely don't agree with you."
6. "I entirely don't agree with you."
These sentences are grammatically correct, although they are not commonly used in English. The addition of "don't" in these sentences introduces a negation after the adverb. This means that you are expressing a complete disagreement, as in the previous set of sentences, but with the added emphasis that you absolutely do not agree with the other person.

In terms of the difference in meaning between sentences 1-3 and 4-6, the main distinction is that the latter group (sentences 4-6) adds an extra emphasis on the negation. It reinforces that there is no agreement whatsoever. It's a more forceful way of expressing your disagreement. However, it is important to note that these sentences may sound less natural in conversation compared to the first set of sentences.

1. "I totally disagree with you." - This means that you do not agree with the person at all.

2. "I completely disagree with you." - This also means that you do not agree with the person at all.
3. "I entirely disagree with you." - This again means that you do not agree with the person at all.

Regarding questions 4-6:
4. "I totally don't agree with you." - This sentence is not grammatically correct. The correct way to express this would be "I don't agree with you at all."

5. "I completely don't agree with you." - This sentence is grammatically correct, but it is not commonly used. It is clearer to say "I don't agree with you at all" instead.

6. "I entirely don't agree with you." - This sentence is grammatically correct, but it may sound a bit awkward or unusual. It is more common to say "I don't agree with you at all" for clarity.

In terms of meaning, both "totally" and "completely" are used to emphasize that there is no agreement whatsoever. The addition of "entirely" does not significantly change the meaning. They all convey the idea of complete disagreement.