Tanto na cozinha quanto no banheiro, eu prefiro deixar tudo limpo.

It creates a balanced pair and means something like both ... and ... here.

So Tanto na cozinha quanto no banheiro means both in the kitchen and in the bathroom.

It is a slightly more structured or emphatic way to connect the two places than simply saying na cozinha e no banheiro.

Because na and no are contractions:

• na = em + a
• no = em + o

Portuguese very often uses the definite article with rooms and places, so:

• em a cozinha → na cozinha
• em o banheiro → no banheiro

Using the contractions is mandatory in normal Portuguese.

Because the nouns have different grammatical gender:

• cozinha is feminine, so it takes a → na cozinha
• banheiro is masculine, so it takes o → no banheiro

This has nothing to do with natural gender; it is just the grammatical gender of the nouns.

Not really. Portuguese often drops subject pronouns when the verb already makes the subject clear.

So both of these are natural:

• Eu prefiro deixar tudo limpo.
• Prefiro deixar tudo limpo.

Including eu can add a little emphasis, contrast, or clarity.

After preferir, Portuguese commonly uses an infinitive when you are talking about preferring an action.

• prefiro deixar tudo limpo = I prefer to leave/keep everything clean

Compare:

• Prefiro café. → preference for a thing
• Prefiro sair cedo. → preference for an action

So deixar is just the action that is being preferred.

Here deixar does not mean simply to go away from something. It means to leave something in a certain state or to keep it that way.

The pattern is:

• deixar + object + adjective

So:

• deixar tudo limpo = to leave everything clean / keep everything clean

Other examples:

• deixar a porta aberta = leave the door open
• deixar a casa arrumada = leave the house tidy

Because tudo normally takes a masculine singular adjective.

So you say:

• tudo limpo
• tudo pronto
• tudo certo

Even if the things included are mixed or not specifically named, tudo stays grammatically singular and masculine for agreement purposes.

It describes tudo, not eu.

In deixar tudo limpo:

• tudo is the object
• limpo is describing the state of tudo

So the idea is not I am clean, but everything is left clean.

Yes. Na cozinha e no banheiro is perfectly natural.

The difference is mostly nuance:

• na cozinha e no banheiro = simple coordination
• tanto na cozinha quanto no banheiro = more balanced, slightly more emphatic, closer to both in the kitchen and in the bathroom

Both are correct.

Because Tanto na cozinha quanto no banheiro is a fronted introductory phrase placed before the main clause.

The comma helps separate that opening phrase from the main statement:

• Tanto na cozinha quanto no banheiro, eu prefiro deixar tudo limpo.

In writing, this is very natural and clear. Without the comma, the sentence would still likely be understood, but the comma is the better choice here.

Yes. Portuguese allows some flexibility.

For example:

• Eu prefiro deixar tudo limpo tanto na cozinha quanto no banheiro.

This is also understandable and natural. The original version puts the location phrase first, which gives it a little more emphasis:

• As for both the kitchen and the bathroom, I prefer to keep everything clean.

So the original word order highlights the two places before stating the preference.

Not exactly.

• limpar tudo focuses on the action of cleaning everything
• deixar tudo limpo focuses on the result: everything ends up clean

So deixar tudo limpo can suggest leave/keep everything clean, while limpar tudo is more directly clean everything.

In many contexts they may be close, but the emphasis is different.