Ο διαχειριστής μας είπε ότι η θέρμανση δεν δουλεύει σήμερα.

Ο is the masculine singular definite article, meaning the.

So:

• ο διαχειριστής = the manager / the building manager

In Greek, the definite article is used very often, even in places where English might sometimes leave it out. In a normal sentence like this, ο διαχειριστής sounds natural and complete.

Literally, διαχειριστής means manager or administrator, but in everyday Greek it often refers to the building manager / superintendent / person responsible for an apartment building.

So in this sentence, it probably does not mean a company manager. It most likely means the person who manages the apartment building.

Grammatically:

• διαχειριστής = masculine singular noun
• dictionary form: ο διαχειριστής

μας here means us.

In μας είπε, it means:

• είπε = said / told
• μας είπε = told us

This μας is an unstressed object pronoun. Greek often places these short object pronouns before the verb:

• μου είπε = he/she told me
• μας είπε = he/she told us
• τους είπε = he/she told them

So the structure is literally something like:

• The manager us told...

but in natural English: The manager told us...

είπε is the aorist form of λέω, and here it means said or told as a completed event in the past.

So:

• λέει = he/she says / is saying
• έλεγε = he/she was saying / used to say
• είπε = he/she said / told

In this sentence, the speaker is referring to one completed act of speaking, so είπε is the natural choice.

ότι means that and introduces a subordinate clause.

So:

• μας είπε ότι... = he told us that...

Greek often uses ότι the same way English uses that after verbs like say, know, think, etc.

Examples:

• Ξέρω ότι έχεις δίκιο. = I know that you are right.
• Νομίζω ότι θα έρθει. = I think that he will come.

In casual speech, ότι can sometimes be omitted, but including it is very common and clear.

No. They are different words.

• ότι = that
• ό,τι = whatever / anything that

In your sentence, it must be ότι, because it introduces what the manager said:

• μας είπε ότι... = he told us that...

Compare:

• Πάρε ό,τι θέλεις. = Take whatever you want.

The comma in ό,τι matters.

η θέρμανση means the heating.

• η = feminine singular definite article
• θέρμανση = feminine noun

So the noun is grammatically feminine, which is why it takes η.

This word refers to heating as a system or service, not the act of heating something with your hands or on a stove.

Dictionary form:

• η θέρμανση

Yes. δουλεύει literally means works / is working, and Greek uses δουλεύω very naturally for machines, systems, devices, and services.

So:

• Η θέρμανση δεν δουλεύει. = The heating isn't working.
• Το ασανσέρ δεν δουλεύει. = The elevator isn't working.
• Το ίντερνετ δεν δουλεύει. = The internet isn't working.

This is very common everyday Greek.

δεν is the normal negation used with verbs in the indicative mood.

So:

• δουλεύει = it works / it is working
• δεν δουλεύει = it does not work / it isn't working

Greek has two main negative particles:

• δεν for indicative verbs
• μη(ν) for subjunctive, imperatives, and some other structures

Here, this is a straightforward statement, so δεν is correct.

Yes, δουλεύει is present tense.

Greek keeps the tense that matches the situation being described. The manager spoke in the past, but what he said concerns today's current situation, so present tense is natural:

• μας είπε = he told us
• η θέρμανση δεν δουλεύει σήμερα = the heating is not working today

This is similar to English:

• He told us that the heating isn’t working today.

You could also sometimes see past-tense backshifting in English, but Greek very often keeps the tense that reflects the actual time of the situation.

σήμερα means today.

It is placed at the end because Greek word order is fairly flexible, and putting time expressions at the end is very common.

So:

• Η θέρμανση δεν δουλεύει σήμερα. = The heating isn’t working today.

You could also hear:

• Σήμερα η θέρμανση δεν δουλεύει.

Both are possible. The version in your sentence sounds very natural and neutral.

The sentence is:

• Ο διαχειριστής μας είπε ότι η θέρμανση δεν δουλεύει σήμερα.

A useful breakdown is:

• Ο διαχειριστής = the manager
• μας είπε = told us
• ότι = that
• η θέρμανση = the heating
• δεν δουλεύει = is not working
• σήμερα = today

So the structure is roughly:

Subject + object pronoun + verb + that-clause

Inside the that-clause:

Subject + negation + verb + time expression

This is a very normal Greek sentence structure.

A rough pronunciation guide is:

O dhi-a-khi-ri-STIS mas EE-pe Ó-ti i THÉR-man-si dhen dhu-LÉ-vi SÍ-me-ra

A few notes:

• θ sounds like th in think
• δ sounds like th in this
• χ is a throaty sound, like the ch in German Bach or Scottish loch
• Stress matters a lot in Greek:
  • διαχειριστής
  • είπε
  • θέρμανση
  • δουλεύει
  • σήμερα

Yes. In this sentence, English naturally prefers told us because Greek has an indirect object pronoun:

• μας είπε = literally said to us / told us

So both ideas are present, but the best natural English translation is usually:

• The manager told us that the heating isn’t working today.

Without μας, it would be closer to just said:

• Ο διαχειριστής είπε ότι... = The manager said that...