two floors of restaurants

two floors of restaurants是指两层楼上有很多饭店，如果想表达一个饭店有两层楼，可以说a restaurant of two floors.

饭店的两层楼。
The second floor of restaurant

指饭店的那两层楼

The second floor of restaurant: 饭店的二楼
Two floors of the restaurant: 那饭店的两层楼
Two floors of restaurants: 两层楼房都是（不同的）饭店。如果单要理解这句话，可以想像一些美食城，每一层都有不同的美食店。

是指两个饭店的地板

This building has two floors of restaurants.
这幢大厦有两层楼是饭店。

The second floor of the restaurant.
饭店的2楼。

The restaurant is on the second floor of the building.
饭店在大厦的2楼。