ossi2612 Hi. Sorry to hear You were sick and I hope everything is ok now. And sorry for missing this thread as well. Not sure why it happened, but I'm back to it now.
As I've visited Your site I can see You have already replaced all custom fonts with Arial. That's good because we can do the easiest thing now and add custom fonts. First You need to create them. Google Fonts page allows a download of those fonts
You will get a .ttf format (You may have also has a font in this format or any other from differtn location than google font). Take this file and use it to generate a custom font here https://www.fontsquirrel.com/tools/webfont-generator it's one of availage font generators, one I use the most, but You can look for other.
It will generate a package, which You will have to upload to template's /fonts folder. For example creating a path:
/templates/fitnes_center/fonts/robato/
When You will have fonts uploaded in template's settings in joomla panel look for an option: "Script To Be Appended Inside Of The <Head> Area" and add this code there:
<link rel="stylesheet" href="templates/fitnes_center/fonts/robato/stylesheet.css" type="text/css">
of course the css file may be named differently, so please pay attention to it.