Show Options based on previous selection

Hello Everyone. New User here of google/excel/appsheet

I am trying to setup in a transaction form for my manufacturing inventory app.

Based on Order Type I want Order Number, Person or Company and Product or Raw Material to change

When PURCHASE is selected (This is when I buy raw material)

Order Number = P1000 sequential (only I will be using the app so no worries about sequential issue)

Person or Company = List of Suppliers (From Customers table)

Product or Raw Material = Raw Materials List (From my Raw Materials table)

I also want the ability to add more Raw Materials because I might buy various Raw Materials
from the same Supplier at different quantities and different prices

I think if I am able to get some guidance to do this I would be able to figure out the other Order Types

Any help will be greatly appreciated