I'm having some trouble distinguishing [ɐ] and [a]. In fast speech I usually pronounce [ɐ] like [a]. Such as Алáния or Голосá. Does it really matter?
From what I see when communicating with people learning Russian is that while pronunciation is definitely important factor it's not the most important one. Decent grammar is crucial.
As of phonetics it's enough to be able pronounce the "basic" set of sounds. I assure you that the majority of Russian native speakers does not even aware that there are more than one "a"-like or "о"-like phonemes. Moreover, though modern Russian has no such things like very distinctive dialects - there are some dialectal differences.
For instance, around the Ural Mountains, people are pronouncing vowels noticeably in a very different way compared to one you can hear in, say, Central Region. And they don't give a flying anything whether their Russian is "normal" or not ;)
I encourage you to practice and do not care about subtle phonetics issues so far.
According to my experience, following common issues are disturbing while speaking Russian:
- Using English or French-like "r" instead of "р" (картавость);
- Messing "c" with "ш" (шепелявость);
- Pronouncing "тя", "ме" and etc. as "тья", "мье" (excessive iotizing);
- Saying "и" instead of "ы".
In everyday communication, most of other issues sound sweet. If you go wrong with "а", some people won't even notice, and the rest would think it's adorable. Furthermore, as lots of Russian think that Russian language is the most hard for learning, they will not blame you even for the issues listed above. Surely they would notice that you have an accent, but they would not think that you are low-educated or something like that. They would rather feel themselves flattered, since you have spent so much time and efforts to study their language.
However, they won’t be so pleased if you do a grammar error. Obviously grammar error means that you have not spent so much time studying.
In fast speech I usually pronounce [ɐ] like [a]
I guess that's because your "fast speech" is not so fast, in fact. If you will ever talk Russian with the same tempo, as native speakers do, you will have to apply a vowel reduction extensively. Actually that's the only why we need a reduction at all - to be able to speak fast. And, maybe, you do reduce your speech sometimes, without even noticing - that's how we all do that, and that's perfectly OK too. So just learn "better Russian" and one day you'll get "faster Russian" for free.
In fact, it doesn't matter as much as you might think. If you pronounce stressed like unstressed (or, on the contrary, unstressed like stressed), most of russians will understand you. But sometimes it's difficult enough to understand person, whose native language isn't Russian, so it will be better, if you try to pronounce А letter correctly. When the syllable is stressed, sound is not as long as english "ah", but very close to that. And in the unstressed syllables it's shorter and sounds like "u" in "cut", "nut" etc. Talk Russian, keep on training and you'll get it :)