Remove space on the left

Hi all!

Since the blank space on the left doesn’t really have a function on pages, I’d like to remove it. I tried the css code below, that appeared to work for someone else, but nothing happens.

.single-post .post-inner {
width: 100%;
}

Using a relative position appears to be working at first, but will mess up the layout once the screen gets smaller.

Hopefully someone found a way and can help me! ??

Thanks!