How change css class on scroll?

I checked this guide https://www.youtube.com/watch?v=JMsNslI8KoY&ab_channel=BrianDesign But its not exactly what I want I have site-restaurant and I have food categories (main dishes deserts drinks etc.) And this data in index.ts file and it should dependency on how much food in each food category I have (for example in main I have more in drinks I have less items and when I want add smth or remove I should change this variable) Aaa Its hard a bit to describe in 1 sentence but if you did smth similar please spent some your time for me and explain me in voice how I can do it Something very similar to my case you can find here - https://www.lieferando.de/speisekarte/aeaedjeschoss