author custom color, font, size

1. Additional CSS in the Customizer > Additional CSS is stored in the Theme Options. Updating the theme WILL NOT remove that CSS. If you switch themes then the CSS won't be in the new theme, but it will be there if you switch back to GP. The Code Snippets method is also a viable method for adding CSS, although personally i only use that for PHP functions when a Child Theme is not available.

2. Adding Google fonts locally will remove the request to Google servers to download the font. This may improve site performance.

thank you david !!!
i will follow your directions then and i will use the theme's css and add the google fonts locally.
and generally thank you everybody because you all helped in this ticket !!

Glad we could be of help!