Digital B&W photos can be tricky to achieve a good light balance, Yegor.
I find that most of the simple auto methods either desaturate the colour image or just use the green channel; and both of these tend to lose a lot of contrast.
There are several methods for converting colour photos to B&W. I mostly use the Channel Mixer method plus a few adjustment layers to stretch the contrast range a bit further. But I have recently found that the best of the 'auto' conversion software can produce good results if you play around with the tint adjustments; plus sometimes a little bit of extra 'clever stuff'.
What is available will depend on your software.
Some of our monochrome specialists will probably be able to explain the various methods much better than I can; but I will look for some tutorials which I have found useful.
ps. I thought that your first 2 examples were rather difficult subjects to start with, but the third one is looking good.
This is the chief tutorial that I found to be useful
http://www.computer-darkroom.com/tut...torial_2_1.htm