I want to change the text font family without child theme

You can follow this guide (video) which doesn't require a child theme:
https://docs.generatepress.com/article/adding-local-fonts/

Thanks a lot. I will. But do you understand, I need to get off the google font family, It delay almost 2 seconds, the page speed, of my web site. It is too much for just simple fonts style. That is what I need I want to use system font family, from windows system
I will try it. Thanks

If you want to use system font, you just need to remove all the fonts you added at customizer > typography > font manager.

If no specific fonts are set elsewhere, your site will use system default fonts.