"Yo estoy en el primer piso."
Traducción:I am on the first floor.
No, sorry. That sounds strange. "Level" = The table is level. The door is level. In a building: first floor, second floor, third floor, fourth floor, etc.
In English 'level' IS also used for 'floor' - in some buildings the word 'Level' is used on their signs Level 1, Level 2, etc (though perhaps more common in multi storey car parks)