Center top logo

Hi, I'm doing a new website in Squarespace, trying to get the meny situation of "centered logo, menu on the right". I'm trying to use custom CSS and sometimes it works? But only in "edit CSS" mode? Right now it's not happening at all. Does anyone have a simple fix for this? Trying to center the logo on a design with the menu on the right.

The code:

.header-title-logo {
  display: flex;
  justify-content: center;
}
.header-title-logo img {
    width: auto;
    max-width: 100%;
    max-height: 90px;
      margin: auto;

}

This solution:

margin-left:150%;

seems to work but only in the editing-space? As soon as I save and exit it's no longer centered (but it is saved, and will center if I enter Custom CSS). 

Hi. Can you share site url? We can help easier