Δεν ξέρω αν συμφέρει να πάμε με ταξί τώρα.

Here αν means whether / if and introduces an indirect question:

Δεν ξέρω αν... = I don't know whether... / I don't know if...

It does not mean the kind of if used in a condition like If it rains, we'll stay home. In this sentence, it means whether it is worth it / whether it makes sense.

Δεν ξέρω means I don't know.

Greek usually places the negative particle δεν directly before the verb:

• ξέρω = I know
• δεν ξέρω = I don't know

So the sentence literally begins with I don't know whether...

συμφέρει comes from συμφέρω and in everyday Greek it often means something like:

• it is worth it
• it is advantageous
• it makes financial/practical sense
• it is a good idea, considering the cost or benefit

In this sentence, the idea is basically: I don't know if it makes sense / if it's worth it for us to go by taxi now.

Very often, συμφέρει has a practical or financial flavor, not just a general good idea.

Because συμφέρει is being used impersonally here.

Greek often uses certain verbs in the 3rd person singular to mean it is ...:

• συμφέρει = it is worth it / it is advantageous
• πρέπει = it is necessary / one must
• φαίνεται = it seems

So even though we are the ones going, the structure is not we are worth-it-going. It is:

I don't know whether it is worth it for us to go by taxi now.

That is why συμφέρει stays in the 3rd person singular.

να introduces a subordinate clause with the Greek subjunctive form.

After many verbs and expressions, Greek uses να + verb where English might use an infinitive:

• θέλω να πάω = I want to go
• μπορώ να έρθω = I can come
• συμφέρει να πάμε = it is worth it to go / for us to go

Since Modern Greek does not use an infinitive the way English does, να πάμε does the job that to go does in English.

Here πάμε is the 1st person plural form of πηγαίνω / πάω in the subjunctive environment after να:

• να πάω = for me to go
• να πας = for you to go
• να πάει = for him/her/it to go
• να πάμε = for us to go

So να πάμε means for us to go or simply to go when the subject is we.

Do not confuse this with the everyday standalone πάμε!, which can mean let's go! In your sentence, it is just part of the clause να πάμε.

με means with / by, and with means of transport Greek often uses με:

• με λεωφορείο = by bus
• με τρένο = by train
• με αυτοκίνητο = by car
• με ταξί = by taxi

So να πάμε με ταξί means to go by taxi.

Both can exist, but they do not mean exactly the same thing.

• με ταξί = by taxi in a general sense, focusing on the means of transport
• με το ταξί = with the taxi / by the taxi, often sounding more specific or referring to a particular taxi or a more definite situation

In your sentence, με ταξί is the natural general way to say by taxi.

Yes, Greek word order is fairly flexible.

τώρα means now, and placing it at the end is completely natural:

• Δεν ξέρω αν συμφέρει να πάμε με ταξί τώρα.

You could also hear:

• Δεν ξέρω αν τώρα συμφέρει να πάμε με ταξί.
• Τώρα δεν ξέρω αν συμφέρει να πάμε με ταξί.

But these may shift the emphasis slightly. The original sentence sounds natural and neutral.

In this sentence, αν and εάν mean the same thing: if / whether.

• αν is more common in everyday speech
• εάν is a bit more formal or careful

So:

• Δεν ξέρω αν συμφέρει...
• Δεν ξέρω εάν συμφέρει...

Both are correct, but αν is the more typical spoken choice.

Yes. In informal spoken Greek, άμα is often used where αν would also work:

• Δεν ξέρω άμα συμφέρει να πάμε με ταξί τώρα.

This is common in conversation, but αν is usually the safer and more standard form for learners.

Usually it strongly suggests a practical advantage, often including cost, but it can be broader than money alone.

Depending on context, it may mean:

• it is cheaper or financially reasonable
• it saves enough time to be worth the cost
• it is the most practical option overall

So the sentence does not have to mean only Is it cheap enough? It can also mean Is taking a taxi the smart/practical choice right now?

Not in this structure.

After να, Greek uses the subjunctive-type form:

• να πάμε

You would not normally say:

• να πηγαίνουμε here

Also, πηγαίνουμε and πάμε can differ in aspect and style. In this sentence, να πάμε is the natural choice for to go / for us to go as a single action.

The sentence breaks down like this:

• Δεν ξέρω = I don't know
• αν = whether / if
• συμφέρει = it is worth it / it makes sense
• να πάμε = for us to go
• με ταξί = by taxi
• τώρα = now

So the grammar is:

Δεν ξέρω + αν + impersonal verb + να clause

This is a very common Greek pattern:

• Δεν ξέρω αν πρέπει να φύγουμε. = I don't know if we should leave.
• Δεν ξέρω αν αξίζει να το αγοράσω. = I don't know if it's worth buying it.
• Δεν ξέρω αν συμφέρει να πάμε με ταξί τώρα. = I don't know if it's worth going by taxi now.