How to add Google fonts locally
Use the google-webfonts-helper or a similar tool to download all possible font formats (only *.woff won't be enough regarding cross-browser compatibility).
Store the font files somewhere in your theme, maybe in a subfolder called /fonts.
Use @font-face in your CSS to load the fonts as described in this brilliant CSS-Tricks article: Using @font-face





@font-face {
  font-family: 'MyWebFont';
  src: url('../fonts/webfont.eot'); /* IE9 Compat Modes */
  src: url('../fonts/webfont.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
       url('../fonts/webfont.woff2') format('woff2'), /* Super Modern Browsers */
       url('../fonts/webfont.woff') format('woff'), /* Pretty Modern Browsers */
       url('../fonts/webfont.ttf')  format('truetype'), /* Safari, Android, iOS */
       url('../fonts/webfont.svg#svgFontName') format('svg'); /* Legacy iOS */
}

body {
  font-family: 'MyWebFont', SomeFallbackFont, sans-serif;
}