I've got a problem in my responsive design, I've written top: 0 and bottom: initial to the .header class, So, My website is not showing any data

Especially my website is showing up in 768px, I saw I've written the responsive code in 768px that top: 0; and bottom: initial in .header-class, Another problem is 568px's responsive design. I've written .header-content order: 0; This is also making a problem in my header section when I make it responsive. I've attached a google drive file below with a zip file. Please check the code and give me the answers.

https://drive.google.com/file/d/1cv5ddoqSW1WzMPf8uSZlr5f6fvZQFWET/view?usp=sharing