Limpei a lama das botas antes de entrar, sem que a sala ficasse suja.

Portuguese often drops subject pronouns when the verb ending already makes the subject clear.

• limpei = I cleaned
• the ending -ei shows 1st person singular in the pretérito perfeito (simple past)

So (Eu) limpei is possible, but eu is usually omitted unless the speaker wants emphasis or contrast.

Limpei is the pretérito perfeito of limpar.

It is used for a completed action in the past. Here, the cleaning happened before the next action.

Compare:

• limpei = I cleaned, I did clean
• limpava = I was cleaning / I used to clean

So limpei fits because the speaker is talking about one finished action.

Portuguese uses definite articles more often than English does.

So a lama is very natural here, even though English might simply say mud. In this sentence, it refers to the specific mud that was on the boots.

This is very common in Portuguese:

• a lama
• as botas
• a sala

English often leaves these articles out where Portuguese keeps them.

Das is a contraction of:

• de + as = das

So a lama das botas literally looks like the mud of the boots, but in natural English it means something like:

• the mud from the boots
• the mud off the boots

It does not have to mean possession in a strict sense. It often just shows the source or connection.

Because the subject is the same as in the main clause.

• Limpei... antes de entrar = I cleaned ... before entering

When the same person does both actions, Portuguese usually uses antes de + infinitive.

If you want to name or stress the subject, you can use the personal infinitive:

• antes de eu entrar

That is grammatical, but here it is unnecessary because the subject is already obvious.

Because entrar can be used on its own when the place is clear from context.

Here, the sentence already mentions a sala, so the idea of entering the room/house/building is easy to understand. Portuguese, like English, often omits the destination when it is obvious.

So antes de entrar simply means before going in / before entering.

Sem que introduces an idea like:

• without ...
• without letting ...
• so that ... not

In this sentence, it links the first action to the result that was avoided.

Structure:

• sem que + subjunctive

So sem que a sala ficasse suja means that the room did not end up getting dirty as a result.

Because sem que normally requires the subjunctive.

The subjunctive is used here because the clause expresses something that is:

• not presented as a simple fact on its own
• dependent on the first action
• avoided, prevented, or only potential

So after sem que, Portuguese does not normally use the regular indicative form here.

Ficasse is the imperfect subjunctive of ficar.

This is used because the main verb is in the past:

• Limpei ... sem que a sala ficasse suja

A useful comparison:

• present-time main clause: Limpo a lama ... sem que a sala fique suja
• past-time main clause: Limpei a lama ... sem que a sala ficasse suja

So the tense of the subjunctive shifts to match the past context.

Because ficar + adjective often means to become or to end up in a certain state.

• ficar suja = become dirty / get dirty
• estar suja = be dirty

Here the idea is not that the room already was dirty, but that the speaker prevented it from becoming dirty. That is why ficar is the natural choice.

Because the adjective agrees with a sala.

• sala is feminine singular
• so the adjective must also be feminine singular: suja

Compare:

• o chão sujo
• a sala suja
• as botas sujas

This kind of adjective agreement is essential in Portuguese.

Yes. That would also be natural.

For example:

• Limpei a lama das botas antes de entrar, para a sala não ficar suja.

This version sounds more directly like a purpose clause: I did it so that the room would not get dirty.

The original sem que a sala ficasse suja feels slightly more like:

• without the room getting dirty
• in such a way that the room did not end up dirty

Both are good, but the nuance is a little different.

Yes, it is natural and standard here.

The comma separates the main clause from the following subordinate clause:

• Limpei a lama das botas antes de entrar,
• sem que a sala ficasse suja.

This makes the sentence easier to read and reflects the pause between the main action and the added result/purpose idea. In normal writing, the comma is the expected choice here.