Some issues on new site

Hi there, our new site is almost ready :-). I have a small issue, I hope you can help with:

I've added some custom fonts as you described in the documentation (https://docs.generatepress.com/article/adding-local-fonts/). In Safari and Firefox Montserrat is not properly displayed, it shows something like "Times New Roman" instead. You can see it in the Footer for example.

I hope you have an idea what I am doing wrong.