responsive chat app

hi there thank you guys your comment is really helping me i have met two problem while doing this project the first one is while i was trying to design that curve background thing i used :: after for the left one and ::before for the right and it was perfect for the desktop design but when it comes to mobile phone idk why it was adding extra space to body even i made bottom 0 and when i made it negative number i mean percent it add extra horizontal scrollbar and when i make the right negative it also add extra space at the bottom of the body i dont know i try to figure it out but i cant any help? the other is i cant give margin-bottom please help me out and any comment and suggestion really appreciated thanks!