Add logo between site name and tag line

I’ve been struggling with figuring out where to insert the code, that displays the logo.

I’m using the theme “twenty-fifteen” and I’ve added a child-theme to it. There are similar solutions in the forums for adding a logo to the twenty-fifteen theme, like this, this and this, but I still can’t figure it out. Maybe their setup is a little different and they want a logo somewhere else.
Note: there is a build in option for a logo, but it’s for the entire left side of the page. I just want a logo above/below or between the site name/tagline on the left.

For good measure, here is a picture of the top of the website, running the same theme.

The logo is measuring 300 x 280 and I’ve tried with:

#header h1 a {
padding: 15px 0px 35px 120px;
background: url(https://www.website.com/path/logo.png) no-repeat;
}
#head-desc {
padding-left: 120px;
padding-right: 250px;
}

in the style.css file, but didn’t work.

Any suggestions?