Sliding menu in Button funtion

Hi there, I have this very annoying problem, I’m designing this website for a mate: https://luoluosanimation.com/ and as you can see all pages are in one, if you use the menu on top it’ll take you to the part or the page it’s supposed to take you in a sliding manner, which looks nice.

However, for the buttons that I have under Why Animation and Basic and Works, I can’t seem to code them to also go to the Contact part of the page on a sliding manner, only jump to that part, is there any way I can make it go as smoothly as if going via the menu?

Thank you in advance!