Only flex

Hi, frontend mentor community.

I have many questions after finishing this challenge.

I usually write everything (css and html )before checking the output, however the last challenges that i've completed it doesn't look good when i deploy the repository, it looks totally different.

For this one i used height:800px and width:1440px trying to get a better position or screenshot, but it happened again.

Can you guys help me with this issue that i'v been facing?, i don't know if maybe i'm miss using some measurement or maybe i shouldn't use my monitor to finish the design maybe i should use a different screen or maybe a different px ratio.

Pls help me :3