да нет наверное = no (if somebody use both these words together)
For example:
- May I help you?
-hmm, no,thanks.
- Могу я вам помочь?
-да нет наверное, спасибо. ("да" , “наверное" means here that you thinking . You are not sure may this person help you or not, and you saying -no, I needn't help (да нет наверное))
=)
You need just memorize that it's –no.That’s all)