Αύριο δουλεύω ολόκληρο το απόγευμα.

Because Greek often uses the present tense for a planned or clearly scheduled future action, especially when a time word like αύριο already makes the future meaning clear.

So Αύριο δουλεύω is very natural and means something like Tomorrow I’m working.

Compare:

• Αύριο δουλεύω = Tomorrow I’m working / a planned fact
• Αύριο θα δουλέψω = Tomorrow I will work
• Αύριο θα δουλεύω = Tomorrow I will be working / more emphasis on the ongoing action

In Greek, the verb ending usually already shows the subject.

• δουλεύω = I work / I’m working

So εγώ is usually unnecessary unless you want emphasis or contrast.

For example:

• Αύριο δουλεύω = neutral, natural
• Εγώ αύριο δουλεύω = I’m the one who’s working tomorrow or as for me, I’m working tomorrow

Ολόκληρο means whole, entire, or all of.

So:

• ολόκληρο το απόγευμα = the whole afternoon / all afternoon

It adds the idea that the work lasts through the entire afternoon, not just part of it.

Because ολόκληρο has to agree with το απόγευμα.

Απόγευμα is a neuter noun, so the adjective must also be neuter singular:

• ο ολόκληρος... for a masculine noun
• η ολόκληρη... for a feminine noun
• το ολόκληρο... for a neuter noun

Here:

• το απόγευμα = neuter
• therefore ολόκληρο το απόγευμα

Because Greek often expresses duration of time without a separate word like for.

So:

• δουλεύω ολόκληρο το απόγευμα literally looks like I work the whole afternoon
• but it means I work for the whole afternoon / all afternoon

This is very normal in Greek with time expressions.

Because το απόγευμα is a noun phrase meaning the afternoon, and Greek normally uses the article in this kind of expression.

With the adjective, the full phrase is:

• ολόκληρο το απόγευμα = the whole afternoon

The article το is part of the normal structure here.

Yes. Greek word order is more flexible than English.

The sentence given:

• Αύριο δουλεύω ολόκληρο το απόγευμα

is a very natural, neutral way to say it.

But you could also hear:

• Δουλεύω αύριο ολόκληρο το απόγευμα
• Ολόκληρο το απόγευμα αύριο δουλεύω

These alternatives may sound slightly different in emphasis, but the basic meaning stays the same.

A rough pronunciation guide is:

• Αύριο → AV-rio
• δουλεύω → thoo-LE-vo or dhoo-LE-vo
  The first sound is the th in this
• ολόκληρο → o-LO-kli-ro
• το απόγευμα → to a-PO-ghev-ma

A smoother full version:

• AV-rio thoo-LE-vo o-LO-kli-ro to a-PO-ghev-ma

The stressed syllables are shown by the accent marks in Greek:

• αύριο
• δουλεύω
• ολόκληρο? Actually the stress is on λό: ολόκληρο
• απόγευμα

The version with ολόκληρο is stronger.

• δουλεύω το απόγευμα = I work in the afternoon
• δουλεύω ολόκληρο το απόγευμα = I work the whole afternoon / all afternoon

So ολόκληρο emphasizes that the entire afternoon is taken up.

Yes, but it sounds a bit different.

• δουλεύω is the everyday, very common verb for work
• εργάζομαι is also correct, but often sounds a bit more formal or less conversational

So in normal speech, Αύριο δουλεύω ολόκληρο το απόγευμα is the most natural choice.