Al bany n'hi ha dos, de raspalls, però jo només en trobo un.

Because al is the normal contraction of a + el.

So:

• a + el = al
• a + els = als

In this sentence, al bany means in the bathroom or at the bathroom, depending on context. With places, Catalan often uses a where English uses in or at.

Because hi ha is the standard existential form, meaning there is / there are, and in standard Catalan it stays in the 3rd person singular even when the thing that follows is plural.

So you get:

• Hi ha un raspall = there is one brush
• Hi ha dos raspalls = there are two brushes

This is different from English, where the verb changes between is and are.

You may hear plural forms in some varieties of spoken Catalan, but in standard written Catalan hi ha is the expected form here.

They are doing two different jobs.

• hi ha is the fixed Catalan structure for there is / there are
• en is a pronoun meaning something like of them / some / any / of that thing

So:

• hi ha dos = there are two
• n'hi ha dos = there are two of them

Here, en refers to raspalls.

Also, n' is just the shortened form of en before a vowel:
en hi ha becomes n'hi ha.

This is a common Catalan structure where the quantity comes first, and the noun is added afterward for clarification or emphasis.

So:

• Al bany hi ha dos raspalls = a neutral, straightforward sentence
• Al bany n'hi ha dos, de raspalls = there are two of them, brushes

That final de raspalls helps specify what en refers to.

This kind of structure is often called right dislocation or a partitive structure. It is very natural in Catalan, especially in speech.

The comma reflects the pause before the clarifying noun phrase.

For the same reason: en replaces the noun that is being counted.

So en trobo un means:

• I find one of them
• I find one brush

Catalan normally uses en when a noun is omitted after a number or quantity word.

Compare:

• Només trobo un raspall = I only find one brush
• Només en trobo un = I only find one

Without en, the omitted noun would feel less properly represented in standard Catalan.

Yes. That is a perfectly natural and simpler version.

Your sentence with clitics is a bit more expressive and more characteristically Catalan in its structure:

• Al bany hi ha dos raspalls, però jo només trobo un = straightforward
• Al bany n'hi ha dos, de raspalls, però jo només en trobo un = more discourse-driven, with emphasis on the quantities and on the noun being resumed through pronouns

So the original sentence is not more correct than the simpler one; it is just structured differently.

That is true: Catalan often drops subject pronouns because the verb ending already shows the subject.

So you could say:

• ...però només en trobo un

But jo is included here for contrast or emphasis:

• ...però jo només en trobo un

It highlights I — as if saying but I only find one.

This is especially common after però, where the speaker is setting up a contrast.

Because raspall is a masculine noun.

In Catalan:

• un / una agree in gender
• dos / dues also agree in gender

So:

• un raspall
• dos raspalls

But with a feminine noun, you would have:

• una tovallola
• dues tovalloles

That is why this sentence uses dos and un.

Literally, it means I find.

But in context, English often prefers I can only find one, even though Catalan does not need a separate verb like can here.

So:

• només en trobo un = literally I only find one
• natural English: I can only find one

If you really wanted to emphasize ability, you could say something like només en puc trobar un, but that is not necessary here.

Yes, if it is already clear what you are talking about.

For example, if everyone knows the conversation is about brushes, then:

• Al bany n'hi ha dos = there are two in the bathroom

is enough.

The extra de raspalls is only there to clarify or reinforce the noun. So the full sentence is more explicit, but not always necessary.