Υποθέτω ότι δεν συμφέρει να αγοράσω τώρα καινούριο κοστούμι, αφού τον επόμενο μήνα ίσως χρειαστώ τα χρήματα για το ταξίδι.

Ότι introduces a content clause: it means that.

So:

• Υποθέτω ότι... = I suppose that...

In English, that is often optional, but in Greek ότι is very common and natural in this kind of sentence.

You could think of the structure as:

• Υποθέτω = I suppose
• ότι δεν συμφέρει... = that it isn’t worth it / that it doesn’t make sense...

Here συμφέρει is being used impersonally.

Greek often uses verbs like συμφέρει in a structure equivalent to:

• it is worthwhile / it is advantageous / it makes sense

So:

• δεν συμφέρει να αγοράσω...
  = it doesn’t make sense / it isn’t worth it for me to buy...

There is no normal personal subject like I or the suit. It works like English it in it is worth it or it makes sense.

In this sentence, συμφέρει means something like:

• it is worth it
• it is financially sensible
• it makes sense from a practical point of view

It often has a nuance of benefit, especially financial or practical benefit.

So δεν συμφέρει να αγοράσω τώρα καινούριο κοστούμι suggests not just I don’t want to buy one, but more specifically:

• it’s not a smart or economical decision right now

After συμφέρει, Greek normally uses a να-clause.

So:

• συμφέρει να... = it is worth it to... / it makes sense to...

The verb αγοράσω is the aorist subjunctive form of αγοράζω.

Why aorist here? Because the speaker is thinking of a single complete action:

• buying a suit

not an ongoing or repeated action.

So:

• να αγοράσω = to buy / for me to buy (one complete act)

If the sentence were about repeated or continuous action, the present subjunctive might be used instead.

Because after να, Greek uses the subjunctive, not the future marker θα.

So:

• να αγοράσω = for me to buy / to buy
• θα αγοράσω = I will buy

In this sentence, the speaker is not directly saying I will buy. They are saying:

• it doesn’t make sense to buy

That requires the να construction.

Καινούριο agrees with κοστούμι.

• κοστούμι is neuter singular
• so the adjective must also be neuter singular

That gives:

• καινούριο κοστούμι = a new suit

Here it is in the same form as nominative/accusative neuter singular, which is normal because κοστούμι is the object of αγοράσω.

Greek can place adjectives before or after the noun, but before the noun is very common, especially in ordinary descriptive phrases.

So:

• καινούριο κοστούμι = natural and common

You may also see adjective placement after the noun in other contexts, often with a slightly different emphasis or style. But here the pre-noun position is the most straightforward, natural choice.

Yes, αφού can be confusing because it has more than one use.

In this sentence, αφού means:

• since
• because
• given that

So here it introduces the reason:

• αφού τον επόμενο μήνα ίσως χρειαστώ τα χρήματα... = since next month I may need the money...

In other contexts, αφού can also be related to after, but here it clearly means because/since.

Greek often uses the accusative of time for expressions like:

• this week
• next month
• last year

So:

• τον επόμενο μήνα = next month

Literally it looks like the next month, but functionally it means next month.

This is very common in Greek. No preposition is needed.

Because the sentence means next month as a time expression, not in the next month as a location-like phrase.

Greek usually says:

• τον επόμενο μήνα = next month
• την επόμενη εβδομάδα = next week
• την άλλη φορά = next time / another time

Using στον would change the structure and would usually not be the normal way to express this idea here.

After ίσως (maybe / perhaps), Greek can use the subjunctive, and να may be omitted.

So:

• ίσως χρειαστώ
• ίσως να χρειαστώ

Both are possible.

In this sentence, ίσως χρειαστώ is a perfectly natural way to say:

• I may need

This is something learners often notice because Greek usually signals the subjunctive with να, but after ίσως, omission of να is common.

Because the sentence refers to a possible future need, viewed as a single event:

• I may need the money

The form χρειαστώ is the aorist subjunctive form.

Compare:

• χρειάζομαι = I need / I am needing
• να χρειαστώ / ίσως χρειαστώ = to need / may need (single event, future-oriented here)

So the speaker is not describing an ongoing present state, but a possible need that may arise next month.

Yes. It comes from the same verb family, but the forms are not identical in appearance.

Learners often notice:

• present: χρειάζομαι
• aorist/subjunctive-related form: χρειαστώ

This kind of stem change is normal in Greek verbs. So even though the form looks quite different, it still belongs to the same verb meaning to need.

In Modern Greek, χρήματα is normally used in the plural to mean money.

So:

• το χρήμα can exist, but often means money in a more general or abstract sense
• τα χρήματα is the usual everyday way to say the money

In this sentence:

• ίσως χρειαστώ τα χρήματα = I may need the money

That is the normal, natural wording.

Greek uses the definite article more often than English.

So:

• για το ταξίδι = for the trip

The article το is natural here because the speaker has a specific trip in mind.

Greek often includes the article in places where English may or may not use one, so learners should not expect article use to match English exactly.

Here για means:

• for

So:

• τα χρήματα για το ταξίδι = the money for the trip

It shows purpose/use: the money is intended for the trip.

Yes, Greek word order is fairly flexible.

Here:

• να αγοράσω τώρα καινούριο κοστούμι

means to buy a new suit now

But Greek could move τώρα for emphasis, for example:

• να αγοράσω καινούριο κοστούμι τώρα

The chosen position is natural and keeps the timing closely connected to αγοράσω.

Because αφού introduces an explanatory/reason clause:

• since / because I may need the money next month...

The comma helps separate the main statement from the reason that follows. This is standard punctuation in Greek for this kind of sentence.

Yes, very common. It follows a very natural pattern:

• Υποθέτω ότι... = I suppose that...
• δεν συμφέρει να... = it doesn’t make sense to...
• αφού... = since / because...
• ίσως χρειαστώ... = I may need...

So although there are several grammar points inside it, the sentence as a whole is very idiomatic and everyday Greek.