If you have other objects interacting with your company object, and you don't need to care how those objects implement things, you'd go for interface.
Why not use simple properties?
class Company
{
turnover
{
get;set;
}
staffCount
{
get;set;
}
List<product> productList;
}
Class Product
{
int productID;
string productName;
.
.
}</product>
btw, your intention is to learn just OOPs or OOPs on MVC (Asp.net)?
If you would like to learn OOPS, stick with Console Applications that spares you from other framework (MVC) wiring and debugging.