Codes to write so as to let your site to fit screen

Answer 1

you should familiar with relative css units like "%" e.t.c

Answer 2

Use <meta name ="viewport" content="width =device-width">

If you want basic mobile compatibility you can also use media queries.

Answer 3

Hi Fuad, use CSS properties.
your friends are. vh,vw,vmin for width and height.
CSS Flexbox and CSS grid are the modern way to layout your page in a responsive manner