Responsive Web Design using Grid, Flexbox ( love, passion & grit )

Dear Community,

Kindly review the project and give feedback on below

1. I've hard coded width for mobile layout, is this good practice or there is any other way to handle it ?

2. I've hard coded grid columns width and/or row height, is this fine or there are better ways to handle it ?

3. Any other code optimization techniques please suggest

Thanks in advance.