Is there possible to remove only the similar voices as I make a selection on track?
for example, I have some strange sound (lasts half second) about 50 times in my audio file.
I select area of one of that 0.5second voice, and want to remove all sounds (very similar or exactly that) like that.
I know NOISE REDUCTION is something to do that, but is there any better solution, not to affect whole track, but only remove the dublicates of that selected sound?
Not really. There is https://forum.audacityteam.org/t/need-pointers-on-adding-feature-to-search-pattern/33729/3 which isolates similar sounds. You could use that on a duplicate of the track, label the detected sounds with Analyze > Sound Finder…, then use the Edit > Labeled Audio commands to remove the labeled audio in the original track.
But that would remove the voices, shortening the track, not remove some voices from the background, leaving the background and leaving the length the same. And it doesn’t work so well if the voices you want to remove are mixed with other sounds.
You would have to wait for a proper Audio Diff feature.