I feel stupid asking this so late in the lessons, but is the second о in помощь pronounced О or А? I get that the stress is on the first one, but I can't decide what I hear on Duolingo. And it doesn't help that when I check on Forvo that I hear some people reduce the second О, while others don't :/
The unstressed о/а in Russian is actually a Schwa (wikipedia), meaning it's kind of in between, and the sound you'll hear heavily depends on the consonants surrounding it. Here, the previous hard мъ produced by protruding the lips pulls it naturally towards an o sound, whereas the following щ tends to do the opposite (you stretch your lips outwards to let the flow of air through, and that's more conducive to an a sound).
All of this to say, it depends on a lot of factors, and it doesn't matter all that much. I would suggest aiming for a vowel that's sort of in between an o and an a and see how it naturally comes out. That's a suggestion I'd actually extend to any unstressed о/а, because in some cases forcing an a sound can be kind of jarring (my favorite example: пробовал is definitely not pronounced probaval).
The first stressed "o" is really clear to me, and I think that's the important thing - you can kind of mess around with the sound of the unstressed second "o" - that's what happens when you put words like this into forvo.com and get a number of different pronunciations of unstressed "o".
For example: ребёнок. If you listen carefully, you can hear quite a variety of "o" sounds:
That kind of thing happens in a lot of languages - where the key elements in speech are evident, but the less important elements are mushed up. You're still understood, because you get the important things right.
When you think about it, it's quite interesting that someone from New England with a hard Yankee accent can converse with someone from the Deep South with a soft Southern drawl. As long as they use idioms they both know, the differences in pronunciation usually aren't a problem.
What is the phonetic difference that the ь in помощью makes? When I started learning Russian (many years ago) I was told that if it appears before я, ю, е or ё, it signifies a "separation" of the preceding consonant from the vowel, "cancels" the softening effect of the vowel, and makes the consonant get its hard version. Is it so? If so,
(1) Is there even a difference between a soft and a hard pronunciation of щ? (2) In the basic word the щ is (theoretically?) soft, because of the ь. How comes we want to cancel this effect in the declension?