It`s something strange going on with modifying less files. I really tried to work with them, but the case that all of them are mixing before displaying is making me mad 
There is a need to use everytime a very specific selector.
There is even more, when I have tried to change backround colors of some elements it hadn’t worked. And I don’t know the reason of it: Bootstrap Theme - #12 by NateWr
After some experience with less I have found that working with CSS is far more easier in case of OJS.