Do I need media queries if I use flexbox?

It depends on your design actually :)
If you have simple layout, not really.
If you want your mobile ui to look different from desktop, you might need it

Ok, thanks mate. Will add flexbox today and see how it looks.

id say most likely yes. unless your a flexbox pro

watch this video:…

I'm definitely not 😂

Love that guy's videos. Watching now...

yeah, he taught me everything about coding