How do native Spanish speakers speak these similar pairs of words correctly when they speak fast?

I can tell you, as a native argentinian-spanish speaker, that the difference can be told. v is mostly produced -in argentina/uruguay mainly- as a extremely softened v, while b may go either way (b/v) only in cases where the emphasis produces a plosion and it defines b. P in spanish is not so much emphasised as in it happens in english, to be honest, we don't devote so much energy to consonants in general (latin speakers) and mainly stress every word we speak and let vowels be clear. Fast speech is really hard to get in any language. Keep up the practice, Greetings from Bahía Blanca.

English and Spanish contrast consonants in a different way. In English, what are called http://en.wikipedia.org/wiki/Stop_consonant have a twofold contrast: they are http://en.wikipedia.org/wiki/Voiced_consonant so that the vocal chords keep vibrating while they are pronounced (try saying “bee” and see what your vocal chords do, compared to “pee”), while they they also have a contrast by being http://en.wikipedia.org/wiki/Aspiration_(phonetics) or not (a breath is added to the sound). Refer to: In English, this makes plosives contrast this way: Voiced unaspirated — Unvoiced aspirated                              b —  pÊ°                              g —  kÊ°                              d —  tÊ° To elaborate, in Spanish the contrast is by voice, and by plosiveness. In other words, one group of consonants is unvoiced and plosive, but the other is voiced and approximated; that is, pronounced not exactly by letting air out in a ‘popping’ fashion, but as if the lips and mouth were preparing to close the air flow, but instead of doing so just constricted it slightly. Imagine for instance, getting your mouth in the position in which you pronounce the sound /d/, but allowing the air to pass through. Congrats! That is the sound in the word mother—/ð/. This way, Spanish phonology contrasts the following consonants: Voiced approximant — unvoiced plosive unaspirated.                                 β — p   (/β/ sounds a lot like a /v/)                                 É£ — k                                 ð — t Just to complicate things a little bit: The contrast described above is a little simpler than reality. For instance, when you say that you are listening to people pronounce “babebibobú”, “gageguigogú” and “dadedidodú” in Spanish, it’s normal for speakers, at the beginning of an utterance, to pronounce the approximants like plosives. This means that they resemble /b/, /d/, and /g/ in word-initial (and a few other) places. So, a recording of these strings of syllables would likely sound like: /baβeβiβo'βu/ /gaÉ£eÉ£iÉ£o'É£u/ /daðeðiðo'ðu/ A trick, as an Engish speaker then, is to try to stop looking for unvoiced consonants based on their breathyness, which works in English, but not in Spanish. Also, tune into the fact that a word like dado in Spanish will likely be said as if in English it were “datho”. Best of luck learning Spanish!

This is common when we learn new languages. They can pronounce them fast because they're trained. You are pronouncing the consonants in a very rigid way, not allowing your tongue to explore slightly different ways to make the same consonant that would allow you to pronounce them all together in a faster way.

Hi. The Spanish don't try to speak fast, the fact is that the Spanish doesn't notice that we talk fast.