Ο ιδιοκτήτης μού είπε ότι πριν υπογράψω πρέπει να διαβάσω ήρεμα το συμβόλαιο.

The accent helps show that μού belongs with the verb είπε and means to me.

So:

• Ο ιδιοκτήτης μού είπε = The landlord/owner told me
• Ο ιδιοκτήτης μου είπε can be read as My landlord said/told

In writing, the accent is often used to prevent that ambiguity.

Μού is the weak genitive form of εγώ.

In Modern Greek, these weak genitive pronouns are often used for indirect objects:

• μου = to me / my
• σου = to you / your
• του / της = to him, to her / his, her

So μού είπε literally means said to me, which English usually translates as told me.

Είπε is the aorist form of λέω.

• λέω = I say / I tell
• είπε = he/she said / told

The aorist is used because this is a completed past event: the owner told me something at a particular moment.

Greek λέω covers both ideas, and the structure tells you which English verb sounds more natural.

• είπε ότι... = he said that...
• μου είπε ότι... = he told me that...

Because this sentence includes μού = to me, English naturally uses told me.

Ότι introduces a content clause, like English that.

So:

• μού είπε ότι... = he told me that...

It connects the main clause to what was said.

Also, Greek often allows πως instead of ότι in this kind of sentence, and in casual speech the conjunction may sometimes be omitted. But ότι is completely standard and clear.

Because ο ιδιοκτήτης is only the subject of είπε.

Inside the subordinate clause, the person who will sign and read is me, not the owner. Greek does not need an explicit εγώ here, because the verb endings already show first person singular:

• υπογράψω = I sign
• διαβάσω = I read

So the sentence means that the owner told me what I need to do.

Nothing is missing.

After πριν, Greek very often uses this verb form directly:

• πριν υπογράψω = before I sign

You can also hear πριν να υπογράψω, and it is possible, but πριν υπογράψω is very common and natural.

They are traditionally called aorist subjunctive forms. In some modern grammars they are described as perfective non-past forms.

They are not future by themselves. Instead, they appear after words such as:

• να
• θα
• πριν

In this sentence, they refer to single complete actions:

• υπογράψω = sign, as one whole act
• διαβάσω = read, as one whole act

Because διαβάσω presents the action as a complete whole: read through the contract.

That fits this context well, because the speaker is talking about one specific act before signing.

Compare:

• να διαβάσω = to read it through once / to complete the reading
• να διαβάζω = to be reading / to read habitually or repeatedly

So πρέπει να διαβάσω το συμβόλαιο sounds like I need to read the contract through.

Ήρεμα is an adverb meaning calmly, quietly, or without rushing.

It modifies διαβάσω, so the idea is:

• read the contract calmly
• read the contract at ease, without pressure

It comes from the adjective ήρεμος = calm.

Because it describes how the reading should be done, not the noun συμβόλαιο.

• ήρεμο συμβόλαιο would mean a calm contract, which makes no sense here
• διαβάσω ήρεμα means read calmly

So ήρεμα modifies the verb, which is exactly what adverbs do.

Το συμβόλαιο is the direct object of διαβάσω, so it is in the accusative singular.

It also has the definite article because this is a specific contract, not just any contract. Greek uses the definite article very frequently with specific nouns, often more than English does.

Not completely. Greek word order is fairly flexible.

This sentence uses a very natural, neutral order:

• Ο ιδιοκτήτης μού είπε ότι...

But you could also say:

• Μου είπε ο ιδιοκτήτης ότι...

and the core meaning would stay the same.

What matters most is the grammar shown by the endings and by the clitic pronoun μού near the verb.