Default font-size theme Twentyfourteen?

16px most probably

Then my next question is the following.

I need to change the font-size of H1. A Child-theme as been created. Is it in H1.entry-title{} that I change the font-size for H1? Do I need to change it somewhere else as well

It would be easy for me if you can post your site address

The site address is: https://www.oikoscommunity.org/

selecting h1.entry-title should work for you

It didn’t seem to make a difference. Do you have the code so I can see if the correct code was used.

This should do it:

.entry-title {
    font-size: 16px;
}

I needed to change the H1 so I guess it would be H1.entry-title {
font-size: 16px;
}

And the font-size for H1 that I want to change is in the actual post, not the post title

Will important! make the difference?