Μόλις μπαίνω στο σπίτι, κρεμάω το παλτό μου στην κρεμάστρα πίσω από την πόρτα.

Here μόλις means as soon as or once.

So:

• Μόλις μπαίνω στο σπίτι, ... = As soon as I enter the house / Whenever I come into the house, ...

A useful extra point: μόλις can also mean just in other contexts.

For example:

• Μόλις έφτασα. = I just arrived.

So the exact meaning of μόλις depends on the tense and context.

Because the sentence describes a habitual action or a routine.

Greek uses the present tense here just like English does in sentences such as:

• When I get home, I hang up my coat.

So this sentence does not necessarily mean one action happening right now. It means this is what the speaker normally does.

Compare:

• Μόλις μπαίνω στο σπίτι, κρεμάω το παλτό μου...
  = Whenever/As soon as I come into the house, I hang my coat...
  habitual

• Μόλις μπω στο σπίτι, θα κρεμάσω το παλτό μου...
  = As soon as I enter the house, I will hang my coat...
  one future event

Στο is a contraction of:

• σε + το = στο

So στο σπίτι literally comes from σε το σπίτι, but modern Greek normally contracts it to στο.

This is very common:

• στο = to the / in the / into the for neuter singular
• στη(ν) = to the / in the / into the for feminine singular

In this sentence:

• στο σπίτι = into/in the house
• στην κρεμάστρα = on/to the coat rack

The standard full form is μπαίνω σε + accusative, so:

• μπαίνω στο σπίτι

That is the safest and most standard way to say I go/come into the house.

You may sometimes hear μπαίνω σπίτι in more colloquial speech, but learners should treat μπαίνω στο σπίτι as the normal model.

Because Greek uses the definite article in places where English often does not.

English says:

• I go home
• I’m at home

But Greek usually says:

• πάω σπίτι or πάω στο σπίτι
• είμαι στο σπίτι

So in this sentence, στο σπίτι is completely natural. Greek article usage does not always match English article usage.

In Greek, possessive words like μου (my) usually come after the noun, not before it.

So:

• το παλτό μου = my coat
• η πόρτα μου = my door
• το σπίτι μου = my house/home

Notice also that Greek normally keeps the article:

• το παλτό μου
  not just παλτό μου

If you want extra emphasis, Greek can use δικός:

• το δικό μου παλτό = my own coat / my coat with emphasis

They are all in the accusative.

Breakdown:

• στο σπίτι → σπίτι is accusative after σε
• το παλτό μου → παλτό is accusative as the direct object of κρεμάω
• στην κρεμάστρα → κρεμάστρα is accusative after σε
• από την πόρτα → πόρτα is accusative after από

A useful thing for learners: with many neuter nouns, the nominative and accusative look the same, so:

• το σπίτι
• το παλτό

look unchanged.

But with feminine nouns you can see the accusative article more clearly:

• η πόρτα nominative
• την πόρτα accusative

Πίσω από is a fixed expression meaning behind.

So:

• πίσω από την πόρτα = behind the door

It is common in Greek to use combinations like this:

• μπροστά από = in front of
• δίπλα σε = next to
• μακριά από = far from

So you should learn πίσω από as one unit of meaning, even though it has two words.

Because από takes the accusative in modern Greek.

So:

• από την πόρτα
• από το σπίτι
• από τον φίλο μου

In this sentence:

• πίσω από την πόρτα = behind the door

Even though English just uses door with no visible case marking, Greek shows the case through the article: την.

Yes, κρεμάω is a normal modern Greek verb meaning to hang.

You may also see κρεμώ. These are related forms of the same verb, and both exist in modern Greek usage.

For a learner:

• κρεμάω is very common and perfectly natural.
• κρεμώ is also used, often felt as a shorter variant.

In this sentence:

• κρεμάω το παλτό μου = I hang my coat

Yes. At the beginning of a word, μπ is usually pronounced like b.

So:

• μπαίνω sounds roughly like BEN-oh
  more exactly: BÉ-no

A few useful pronunciation notes from this sentence:

• μπαίνω → b sound at the start
• σπίτι → stress on the first syllable: SPEE-ti
• κρεμάω → stress on μά: kre-MA-o
• πόρτα → stress on πόρ: POR-ta

Yes, Greek word order is fairly flexible.

The given order is natural because it starts with the time clause:

• Μόλις μπαίνω στο σπίτι, κρεμάω το παλτό μου...

That feels like:

• As soon as I come in, I hang my coat...

But Greek could move things around for emphasis. For example:

• Το παλτό μου το κρεμάω στην κρεμάστρα πίσω από την πόρτα.
  = My coat, I hang it on the rack behind the door.

The original sentence is neutral and natural. Different word orders usually change focus or emphasis, not the basic meaning.

Because Μόλις μπαίνω στο σπίτι is a subordinate clause, and the main clause follows it:

• Μόλις μπαίνω στο σπίτι,
• κρεμάω το παλτό μου...

This is similar to English:

• As soon as I enter the house, I hang my coat...

Greek often uses a comma when this kind of introductory clause comes first.

You would normally change the verbs like this:

• Μόλις μπω στο σπίτι, θα κρεμάσω το παλτό μου στην κρεμάστρα πίσω από την πόρτα.

That means:

• As soon as I enter the house, I will hang my coat on the coat rack behind the door.

So the contrast is:

• μπαίνω / κρεμάω → habitual, general
• μπω / θα κρεμάσω → one future event

This is a very useful pattern in Greek.