Very interesting that many Czech words sound exactly like in Russian but mean something different ( False friends ) . e.g. žízeň (thirst) means life in Russian .
I'm not an expert in this by any means as I am just learning Czech myself, but I studied Russian in college, and from what I can hear, 'ň' and other 'soft consonants' are pronounced in Czech very similarly to how they are pronounced in Russian (and possibly other Slavic languages). It's very difficult to describe unless you've had a native speaker explain it to you many times and demonstrate. The best way I can describe it is this: imagine you were about to add the sound 'yee' to the consonant (this goes for ň, d', and t') but stop just short of saying the consonantal 'y' sound. However, forming the consonantal 'y' sound in your palette will create the correct pronunciation of the consonant so that the resonance is closer to your soft palette than your hard.
I would appreciate any corrections and clarifications from native Czech speakers or the Duolingo team.
How is the"ň" pronounced? , is it like the letter "ń" or the letter "ñ"? Cause I'm struggling in pronounciating that single letter.
No, that is not correct. The sound you are describing is used in Czech words banka or maminka.
Ň, on the other hand, is a palatal nasal https://en.wikipedia.org/wiki/Palatal_nasal and it is not present in English at all. See the table in the link for examples from other languages.
This is another case where it would be helpful to have similar words pronounced together to help distinguish between them - in this case for me oni and ony.