Thanks for the link! It looks like you’ve changed your theme files directly, is that right? This is not recommended, as you will lose all your changes every time the theme is updated.
An easy way to add custom CSS is to use the CSS editor included in the Customizer as of WordPress 4.7. Head to Appearance > Customize > Additional CSS to add your custom CSS.
I suggest you move out any CSS overrides into the Customizer and reinstall a fresh copy of Toujours.
Now, I see that you’ve specified a bunch of special fonts here:
font-family: "Century Gothic",CenturyGothic,Muli,Lato,Poppins,sans-serif;
But have you pulled those fonts into your site? Adding custom fonts to a site is a two-step process. First you need to enqueue the font in your site, and only then can you use it with CSS. You are probably only seeing Century Gothic on your desktop if you have that font on your computer. Since that font is likely not installed on your phone, that’s why you’re not seeing it there.
An easy way to enqueue a font is to use a Google Fonts plugin.
https://www.ads-software.com/plugins/search/google+fonts/
Century Gothic is not a Google Font, but Lato is, so you might want to go for that one.
https://fonts.google.com/specimen/Lato
I hope this points you in the right direction – let me know if you get stuck at any step.
