Αν ανοίξω τον απορροφητήρα και το παράθυρο μαζί, η κουζίνα δεν μυρίζει τόσο έντονα.

Because Greek uses ανοίγω very broadly.

In this sentence, the same verb covers both:

• τον απορροφητήρα = turn on the extractor hood
• το παράθυρο = open the window

So Greek is happy to use one verb for both actions, even though English would normally use two different verbs.

After αν, Greek commonly uses a subjunctive form for an open condition like if I open...

Here ανοίξω is the perfective/aorist subjunctive form. It presents the action as a single whole event:

• αν ανοίξω = if I open / if I turn on

Using αν ανοίγω would suggest a more ongoing or repeated action, and it would be less natural here unless extra context made that idea important.

In Greek, you do not use θα in the if-clause after αν:

• correct: αν ανοίξω
• not correct: αν θα ανοίξω

In the main clause, θα is possible if you want a more clearly future result. But here the speaker is stating a general result or usual effect, so the present tense sounds natural:

• η κουζίνα δεν μυρίζει τόσο έντονα

So the sentence feels like a practical observation: when I do this, the kitchen doesn’t smell so strongly.

Because τον απορροφητήρα is the direct object of ανοίξω.

The dictionary form is:

• ο απορροφητήρας = the extractor hood

In the accusative singular, it becomes:

• τον απορροφητήρα

This is normal for many masculine nouns in -ας:

• nominative: ο
• accusative: τον

The two nouns have different genders:

• ο απορροφητήρας = masculine
• το παράθυρο = neuter

So their articles are different in the accusative:

• τον απορροφητήρα
• το παράθυρο

Also, neuter nouns often have the same form in nominative and accusative singular, which is why παράθυρο does not change.

Because Greek normally gives each specific noun its own article.

So:

• τον απορροφητήρα και το παράθυρο

is more natural than trying to use one article for both. This is especially true when the nouns have different genders.

English often says the extractor hood and window, but Greek usually repeats the article more consistently.

Μαζί here means together or at the same time.

It tells you that both actions happen simultaneously:

• turn on the extractor hood
• open the window

So the idea is not just doing both things, but doing them together.

Because η κουζίνα is the subject of μυρίζει.

The kitchen is the thing that smells, so it must be in the nominative:

• η κουζίνα μυρίζει

If it were a direct object, then you would use την κουζίνα.

Here μυρίζει means smells or gives off a smell.

The verb μυρίζω can be used in a few ways:

• Η κουζίνα μυρίζει. = The kitchen smells.
• Η κουζίνα μυρίζει ψάρι. = The kitchen smells of fish.

In your sentence, it is intransitive: the kitchen has a smell.

Here it is an adverb.

It describes how the kitchen smells:

• μυρίζει έντονα = smells strongly / intensely

It does not describe η κουζίνα, so it is not functioning as an adjective here.

The related adjective is:

• έντονος (masculine)
• έντονη (feminine)
• έντονο (neuter)

Τόσο means so / that much, and in a negative sentence it often corresponds to English so or as:

• δεν μυρίζει τόσο έντονα = it doesn’t smell so strongly / as strongly

Greek does not always need an explicit second part like English as ... as ... if the comparison is understood from context.

If you want to make the comparison explicit, Greek adds όσο:

• δεν μυρίζει τόσο έντονα όσο πριν = it doesn’t smell as strongly as before

Yes. Greek word order is flexible.

You could also say:

• Η κουζίνα δεν μυρίζει τόσο έντονα αν ανοίξω τον απορροφητήρα και το παράθυρο μαζί.

The original version is very natural because Greek often puts the if-clause first. That makes the condition clear before the result.