In those two phrases:
да ну and
ну да, the key point for understanding their meaning is that
ну means uncertainty applied on the following thing.
да in the beginning of a phrase (e.g.
да ну) means not agreement but rather emotional emphasis:
да что же это! =
what the hell is going on!?,
да отстань ты =
get off me!.
да ну .. =
I have a very strong emotional concerns\uncertainty about ... (may be strongly negative concerns):
_да_ *ну* тебя =
I have _huge negative_ *concerns* about you =
_да_ *ну* что вы =
I'm _very_ *uncertain* about if you should or should not help me = very polite form of saying
thank you (typical of 'upper class', even little bit obsolete)
- or just
-Пошли в кино! \ -Да ну! meaning
-Let's go to cinema! \ -No I really don't want to! I think that's not goin' worth it!
да means just
ну is applied on
ну да =
yes, but I'm not 100% sure about it (in some cases even meaning that person says
But for some strange reason
ну might also be an emphasis word :) (usually coupled with
уж emphasis) meaning more like
100% this time!, while
да-emphasis means more like just
I am very emotional. For example,
ну уж нет! =
No! (with a very slight
not now meaning)
ну уж теперь ты попался =
уж теперь ты попался =
ну теперь ты попался =
now you're caught!
In fact there are plenty of emphasis-words and they also might combine giving totally opposite meaning, so use them wisely :)
The most complicated probably is
да нет наверное that is translated word-by-word as
yes no maybe, but actually means
I'm very uncertain, but I guess the answer is no.