How to make responsive center using bootstrap3?

Question

Bootstrap

Hi all!
Need pro help. I ask you in advance not to criticize for the question (I can’t solve it, I have already lost my appetite and sleep).
Essence of the question:
There is a website: mikekus.com/portfolio
I want to make a responsive center, like his. So that when viewed on different screens, the number of pictures of the work varied from 4 to 2 and at the same time the place was filled (with the help of the width of these same pictures) to the entire width of the screen. That is: if you view the site on a PC, then the number of pictures in a row went 4 (full width, like here:) , if on a tablet, then the number of pictures in a row went 3 (also full width, like here :) , and if on smartphones and phones - the number of pictures in a row went 2, respectively, also for the entire width of the screen of a particular smartphone, as here :.
I'm just getting started with the bootstrap grid.
I know that I need to read and practice more, but until I solve the problem described above, I will not be able to live normally. So please help. I will be very grateful.
Thanks in advance!

Answer 1

<div class="col-xs-6 col-sm-4 col-md-4 col-lg-3"></div>

Something like this, for example

Answer 2

Here's the center code:
Here's what happens when the screen is col-sm (two images are supposed to stretch to the full width of the screen, but instead there is empty space between them and also empty space on the sides):
And here's another one (some images get better to the neighboring ones on the left and only after that they go down):
Can I prescribe something for the container or for img?