Problem with overlapping HTML section

[Hindfath]

Hi, i have a problem in a website im making, i have two section a and an

that i wraped in a container so i can use flexbox and make it in rows or collum depending on the screen size.
BUT when im on my mobile version my two section are overlapping and i naver had this issue when using flexbox
here’is the coode pen, can someone help me please

booki work in progress

Thank you !