Need to edit left and right padding in mobile responsive view

The white space on the left and right of my content in mobile view is huge, and I need to reduce it. I have tried changing the padding with Live Composer, but the lowest setting is zero – and it’s really huge amount of white space. I have searched for a solution, and this answer helps with vertical space, but not horisontal: https://www.ads-software.com/support/topic/need-to-edit-paddings-but-cant-find-the-given-dslc-lines-on-stylecss-file/

I have tried adding padding-left and padding-right to that code, which lets me Increase the margin, but does not allow me to reduce it to remove the whitespace.