What did I get wrong?

It's not "el casa", "casa" is a feminine noun in spanish, therefore it has to use "la" and not "el"
The Mall- El centro comercial
The Pool-La Piscina
The House-El casa (its supposed to be la casa but whatever)
The Theater-El cine
The Beach-La Playa
The Park-El Parque
The Gym-El Gimnasio