New Post: How to change CSS?

.Detail .Name h1{line-height: 24px;}

I need to know how to change that line, because when on mobile phone, the "Name" line is, when there is not enough space, split in two or more lines and the characters are then partly over one another. That looks very amateuristic

I removed the line in ManagerMenuDefault.xml but that has no effect.

There is no CSS file with the line, but one sees it (the line) as top priority CSS, in Google Chrome F12 developers tools, for the element.