The lack of Hitchhiker's Guide to the Galaxy references here is disappointing.
The singular "полотенце" and the plural "полотенца" sound very similar to me. Is there any difference at all?
Russian nouns (words naming things, people, phenomena) have different genders assigned to them: masculine, feminine, and neuter. На́ша is used with feminine words. На́ше is used with neuter words. Наш is used with masculine words.
На́ши is used with plural nouns, regardless of their gender.
When talking about living people, the gender usually corresponds to their real gender:
- Он на́ш учи́тель 'He is our teacher',
- Она́ на́ша учи́тельница 'She is our teacher'
It doesn't work in 100% cases because masculine words can be used to talk about women. But in general, it's quite logical when talking about people.
When talking about inanimate objects, it gets illogical. Лампа 'lamp' is feminine, but торше́р 'floor-lamp' is masculine. You'll probably need to learn the gender of the noun. Often you can infer it from the form of the word (e.g. most words ending in -а in the Nominative case would be feminine, most words ending in -р would be masculine), but this doesn't work for all the words.
the word 'наши' vocalized like 'nashi', but in another sentence it goes more like 'nashu'.. i dont remember the sentence by the way but it was in previous plural words lesson.. so words pronunciation could change, differ from sentence to sentence or what?
I can't hear the actual audio (I'm using my free-software-only notebook, so I don't have Flash installed here), but жи and ши are pronounced as жы and шы (in fact, жы and шы are never written; we write жи and ши instead).
The pronounciation of «наши» shouldn't change, but since it ends with the sound «ы», which is absent in many of the world's languages, you might hear the closest sound of your language instead. «Ы» is something in-between i and u, so you might hear either. You'll eventually learn to pick up Russian sounds, so please don't get discouraged!
Actually, this phrase may be used e.g. when you've come to visit someone, and you know they've assigned you some towels to use, but not sure where you can find them. Sounds pretty natural to me.
I said, "Where is our towels?" This was not accepted. Is this improper English or colloquialism? Because it felt natural to say. Like "Where's our towels?"
It is improper English because "towels" is plural and needs to be paired with "are". English speakers can butcher the language by shortening phrases in ways such as your suggestion. It's a lazy habit that I'm guilty of this myself, but "Where is our towels?" is still grammatically wrong.