Mobile-first solution using css flex property

What challenges did you encounter, and how did you overcome them?

I learned about using the CSS flex property and media query. When I used the CSS flex property alongside fixed width, my project wasn't centered, but as soon as I removed the fixed width, my project became centered. Also, my mobile version was wonky even though my codes were right. I realised the problem was the order. I had placed the mobile media query before the tablet media query. The solution was to put the mobile media query before the tablet media query.

What specific areas of your project would you like help with?

I currently need help in understanding the relationship between css flex property and fixed width.