Fix font sizes and spacing for smaller screens

[navi-arneja]

Currently, the responsive layouts for smaller screens don't follow the sizes and spaces specified in the designs.

Mobile design: https://www.figma.com/design/iXYfSgMQh3x0MaZS5ciYED/Website-2024?node-id=538-1237&t=vCxBN13nBRs9JfPJ-1

Here's a video. Notice how small the heading text gets and how the spacing breaks down. It happens right at the 640 breakpoint:

Screen.Recording.2024-06-18.at.1.04.52.PM.mov