Breakdown of Tú decoras el salón demasiado rápido.
tú
you (informal singular)
rápido
fast
el salón
the hall / the room (lounge, living room)
demasiado
too much / too
Questions & Answers about Tú decoras el salón demasiado rápido.
Why doesn't 'demasiado' change its ending here?
In this sentence, demasiado is an adverb meaning "too", and it is describing the word rápido (fast). Adverbs never change their gender or number. If demasiado were describing a noun instead (like "too much time" - demasiado tiempo, or "too many houses" - demasiadas casas), it would change its ending to match that noun.
Wait, isn't 'rápido' an adjective? How can it describe an action?
Rápido is a flexible word! It can be an adjective (meaning "fast") or an adverb (meaning "fast" or "quickly"). When it acts as an adverb to describe how an action is done, it is always frozen in the masculine singular form (rápido). You could also use the longer adverb rápidamente, but just saying rápido is extremely common in everyday Spanish.
Does 'salón' refer to a hallway in a house?
Not usually. A salón typically refers to a large room for events (like a banquet hall), a classroom (salón de clases), or a living room. If you want to talk about a narrow hallway or corridor in a building or house, you would use the word pasillo.
Is the word 'Tú' required at the beginning of the sentence?