Css Question - I cant figure out how to make this post title and line height resposnive on phone

I cant figure out how to make this work. I have been trying different things with no luck. I just want to increase the posts entry h1 font size and line height. This issue is , that every time I attempt this change and then check my phone, the font size and line height stay huge and nonresposnive.

This is one of the attempts that had no luck :

.post-cover-title .post-title {
font size: 3.25em;
line-height: 62px;

Here is the link to a post where you can check it out on firebug :

Thank you for any help, I appreciate it.

I asked this same question somewhere else but they did not understand my issue so here was my copy/paste response:

the problem is that when I set the font size to a different font size for the header. Then it is not responsive anymore. Right now the theme defaults to a 50px header font size. I want to make it a 52px header font size. But when I do make it 52px through CSS, and then check it on my phone then I notice that the new 52px font size is no longer adjusting to the new smaller screen size but rather stays too large… vs the defaults 50 px font size that is the default of the theme, which adjust perfectly to a new screen size. So somehow by me targeting it though css it looses all responsiveness for smaller screen sizes.