Thanks @elmannic. So do i understand correctly - that it's not worth to consider any 'shaft side' options because it would not help ?

I've talked to the seller, because he is my friend, lol. He said he felt no discomfort. Also - the previous owner didn't had any issues with not having any curtains and roller blinds on the windows (even in bedroom). I think the previous owners was just insensitive peoples. But, yes, i feel angry at them for not telling me.
My GF says that this sound doesn't bother her also - so i guess thats just me and my psyche:)