Fonts don't work, where am I wrong (Sass, Gulp)?

Question

Fonts

Good day.
I'm making a project with Gulp. Project structure in the screenshot.
A font.sass file was created, where the font was added via @font-face (now it is written as in the screenshot, in quotes, but I tried it with '', and without, and with ../), the file is compiled into fonts.css no problem. I add fonts to main.sass via Dmitrijs Balcers 'app/sass/fonts.sass'. In main.css they are properly compiled and added. In index.html in the head I put the path to the fonts through the link. Does not work. My head is loaded with nonsense and there was a lot of work, rest does not help, I can’t find a mistake. I would be happy to help, if you need more information - I will provide.

Answer 1

@import "fonts.sass"
@import "libs.sass"

It was in these lines that there was an error, the wrong way.

Answer 2

@font-face {
    font-family: 'OpenSans Regular';
    font-weight: 400;
    font-display: auto;
    src: local('Open Sans'), url('../fonts/OpenSans/OpenSansRegular.woff') format('woff');
}

url must be in quotes
For modern browsers, woff2 and woff are sufficient.
Why does lato load in roboto?