Ανοίγω λίγο το παράθυρο όταν η κουζίνα μυρίζει άσχημα.

Here Ανοίγω is natural because the sentence describes a habitual action: something the speaker does whenever a certain situation happens.

• Ανοίγω = I open / I am opening
• in this sentence, it means I open in the sense of I usually open

So:

• Ανοίγω λίγο το παράθυρο όταν... = I open the window a little when/whenever...

If you used ανοίξω, that would usually point to a single, completed action in a different kind of structure, often after particles like να or θα:

• Να ανοίξω το παράθυρο; = Should I open the window?
• Θα ανοίξω το παράθυρο. = I will open the window.

So the present tense here matches the English idea of a routine.

It can mean either one, depending on context.

Greek present tense often covers both:

• I open
• I am opening

In this sentence, because of όταν and the general situation, the meaning is:

• I open the window a little whenever the kitchen smells bad

So here it is best understood as a general/habitual present, not something happening right this second.

Because Greek usually does not need subject pronouns when the verb ending already shows who is doing the action.

• Ανοίγω already means I open
• the ending -ω tells you the subject is I

So Greek commonly says:

• Ανοίγω το παράθυρο = I open the window

You would add εγώ only for emphasis or contrast:

• Εγώ ανοίγω το παράθυρο, όχι εσύ.
  I’m the one opening the window, not you.

Here λίγο means a little or slightly.

It modifies the verb Ανοίγω, so the idea is:

• I open the window a little
• I open the window slightly

So λίγο is acting like an adverb here, not an adjective.

Compare:

• Ανοίγω λίγο το παράθυρο. = I open the window a little.
• Έχω λίγο νερό. = I have a little water.

In both cases λίγο means a little, but its role depends on the sentence.

Because it goes naturally with the verb Ανοίγω:

• Ανοίγω λίγο το παράθυρο = I open the window a little

Greek word order is flexible, but this order is very natural. The λίγο tells us how much the window is opened.

You may also hear slightly different word orders for emphasis, for example:

• Ανοίγω το παράθυρο λίγο
• Λίγο ανοίγω το παράθυρο

But Ανοίγω λίγο το παράθυρο is the most straightforward and neutral here.

Greek uses the definite article much more often than English.

So:

• το παράθυρο = the window

Even where English might sometimes say:

• I open window a little — which is not natural in English anyway
• or simply I open the window

Greek strongly prefers the article here:

• Ανοίγω λίγο το παράθυρο

It sounds normal because the speaker means a specific, understood window in the situation.

It can mean when, but in a sentence about repeated actions like this, it often has the sense of whenever.

So this sentence can be understood as:

• I open the window a little when the kitchen smells bad
• or more naturally in context:
• I open the window a little whenever the kitchen smells bad

That habitual meaning comes from the whole sentence, not from όταν alone.

Because Greek often uses the present tense after όταν when talking about general, repeated, or habitual situations.

• όταν η κουζίνα μυρίζει άσχημα
  = when/whenever the kitchen smells bad

This is not talking about one unique future event. It describes a recurring condition.

So the structure is very natural:

• Ανοίγω ... όταν ... μυρίζει ...

Literally, yes, it is close to the kitchen smells badly, but in natural English we say:

• the kitchen smells bad
• or the kitchen smells bad/awful

In Greek, άσχημα is an adverb and works naturally with μυρίζει:

• μυρίζει άσχημα = smells bad

So don’t translate too mechanically. The natural meaning is simply:

• the kitchen smells bad

Because άσχημα is the adverb form, while άσχημη is an adjective.

Here the word describes how it smells, so Greek uses the adverb:

• μυρίζει άσχημα = it smells bad

Compare:

• άσχημη κουζίνα = an ugly kitchen
  Here άσχημη describes the noun κουζίνα, so it is an adjective.
• η κουζίνα μυρίζει άσχημα = the kitchen smells bad
  Here άσχημα describes the verb μυρίζει, so it is an adverb.

Yes. In Greek, this is a normal way to say that there is a bad smell in the kitchen or that the kitchen smells bad.

The subject is:

• η κουζίνα = the kitchen

The verb is:

• μυρίζει = smells

So literally:

• the kitchen smells bad

English can also express the same idea in other ways:

• The kitchen smells bad
• It smells bad in the kitchen

Greek often uses the first pattern.

Yes, definitely. Greek word order is flexible.

You can say:

• Ανοίγω λίγο το παράθυρο όταν η κουζίνα μυρίζει άσχημα.

Or:

• Όταν η κουζίνα μυρίζει άσχημα, ανοίγω λίγο το παράθυρο.

Both are natural. The second version puts more focus on the condition:

• When the kitchen smells bad, I open the window a little.

So the original sentence is neutral and perfectly normal, but Greek allows reordering for emphasis or style.

You know it from both meaning and structure:

• Ανοίγω is a verb that can take a direct object: you open something
• το παράθυρο is that something

So:

• Ανοίγω το παράθυρο = I open the window

Also, το παράθυρο is in the accusative case, but for neuter nouns like παράθυρο, the nominative and accusative forms are the same:

• nominative: το παράθυρο
• accusative: το παράθυρο

So even though the form does not change, its role is clear from the sentence.

A few useful things:

• Ανοίγω is stressed on -νοί-: a-NOI-go
• λίγο is stressed on λί-: LI-go
• παράθυρο is stressed on ρά: pa-RA-thi-ro
• κουζίνα is stressed on ζί: kou-ZI-na
• μυρίζει is stressed on ρί: mi-RI-zi
• άσχημα is stressed on άσ-: AS-hi-ma

Also:

• γ in Ανοίγω is the Greek gamma sound, not exactly like English g
• θ in παράθυρο sounds like English th in think
• ζ in κουζίνα sounds like z

For a learner, the main thing is to keep the stress in the right place, because Greek stress matters a lot.