Learn Hardcore Russian: В нашем офисе работает уборщица, которая приходит рано утром. - In our office there is a cleaning lady who comes early in the morning.

В нашем офисе работает уборщица focuses on the fact that in our office there is a cleaner (existential meaning: “In our office, there works a cleaner”).
Уборщица работает в нашем офисе would focus more on the cleaner (e.g. “The cleaner works in our office (not somewhere else)”).

So starting with В нашем офисе sounds natural when you are introducing the existence of this cleaner in your office for the first time.

What case are нашем and офисе, and how do we know which endings to use?

Нашем and офисе are in the prepositional case (also called locative), used after в when it means “in/inside” a place.

Nominative: наш офис – our office (dictionary form)
Prepositional: в нашем офисе – in our office

Patterns:

Masculine/neuter adjectives: наш → в нашем (ending -ем)
Masculine nouns like офис: офис → в офисе (ending -е)

So: preposition в (meaning “in a place”) + question “где?” (where?) → use prepositional case: в нашем офисе.

What is the difference between уборщица and уборщик?

Both relate to a person who cleans, but they differ in gender and nuance:

уборщица – grammatically feminine, typically referring to a female cleaner.
уборщик – grammatically masculine, typically referring to a male cleaner.

In many workplaces, if the cleaner is female (which is common), speakers will naturally say уборщица.

Grammatically:

уборщица ends in -а, feminine noun.
уборщик ends in a consonant, masculine noun.

The verb работает doesn’t change its form for gender in the present tense, so it’s the same for both:

работает уборщица / работает уборщик.

Why is которая used here, and why is it in this form?

Которая is a relative pronoun, similar to English who / that, introducing a clause that describes уборщица.

It must agree with the noun it refers to in:

Gender: уборщица is feminine → которая is feminine.
Number: уборщица is singular → которая is singular.
Case: here которая is the subject of приходит, so it is in the nominative case.

So we get:

Feminine, singular, nominative relative pronoun: которая.

Literally: уборщица, которая приходит рано утром – a cleaner who comes early in the morning.

Why is there a comma before которая?

In Russian, a clause introduced by который/которая/которое/которые is normally a separate subordinate clause (a relative clause) and must be set off by commas.

Уборщица, которая приходит рано утром has:

Main clause: В нашем офисе работает уборщица
Relative clause: которая приходит рано утром

Russian punctuation rules require a comma before которая in this structure, even though English does not always show a comma before “who/that” in similar sentences.

Why is приходит used and not ходит, придёт, or пришла?

Each choice gives a different nuance:

приходит – imperfective, directional (“comes, arrives”), usually repeated/habitual action.
- которая приходит рано утром = who comes early in the morning (regularly).
ходит – also imperfective, but non‑directional (“walks/goes around, goes (in general)”); it would sound more like who goes early in the mornings without clear “arrives here” meaning.
придёт – perfective future, one‑time or specific future action: who will come early in the morning (on a particular occasion).
пришла – perfective past: who came early in the morning (on one specific past occasion).

Since the sentence describes a regular habit of the cleaner (what she usually does), приходит is the natural choice.

What does рано утром literally mean, and can we say this in other ways?

Literally:

рано – early
утром – in the morning (instrumental form used in a time expression)

So рано утром = early in the morning.

Very close alternatives:

рано по утрам – early in the mornings (emphasizes regularity a bit more)
рано утром каждый день – early in the morning every day
очень рано утром – very early in the morning

All are natural; the original is the neutral, simple version.

Could we say В нашем офисе есть уборщица, которая приходит рано утром? Is there a difference?

Yes, you can say that; it’s correct.

В нашем офисе работает уборщица… focuses slightly more on her working there, her employment / activity.
В нашем офисе есть уборщица, которая… focuses more on the existence of such a person in the office (there is such a cleaner).

In everyday speech, both are possible. Есть is often omitted when the verb already expresses existence or activity (работает, живёт, стоит, etc.), so В нашем офисе работает уборщица usually sounds more natural.

Can we drop которая and say В нашем офисе работает уборщица, приходит рано утром?

That version is not natural in standard Russian. After the comma, приходит рано утром looks like a separate clause without a clear subject.

To keep one subject, you could say:

В нашем офисе работает уборщица и приходит рано утром.

But even that is ambiguous (it can sound like “someone works in our office and comes early in the morning” with a missing subject in the second part) and stylistically awkward.

Using the relative pronoun которая is the normal, clear way:
В нашем офисе работает уборщица, которая приходит рано утром.

Are there other natural word orders for this sentence in Russian, and how would they change the nuance?

Yes, several are possible, with different emphasis:

Уборщица, которая приходит рано утром, работает в нашем офисе.
– Emphasis on this particular cleaner (maybe contrasting her with others).
В нашем офисе уборщица работает, которая приходит рано утром.
– Possible but sounds more stylistic/poetic or slightly clumsy in everyday speech.
Уборщица работает в нашем офисе, она приходит рано утром.
– Two separate sentences joined by a comma (strictly speaking, should be … офисе. Она приходит …). Emphasizes two facts in sequence: she works there; she comes early.

The original В нашем офисе работает уборщица, которая приходит рано утром is the most neutral and natural way to introduce this information.