Well, I've inverted whole image and besides normal map look like casual normal map now(blue) , it made no difference, so it still like on last picture posted. Then I tried different variation with a channels like - invert red and then invert whole image, same with green and vise versa. I did even tried to flip image lol, but that was just desperate trial. Iooks like promblem is deeper than just invert ,but it looks better than without it anyway. I feel shame to upload work in that kinda state, but still gonna use it for myself (cause can't stand oversized weapons). Thank you for involvment, it still helped somehow.