Είναι καλό να έχουμε βάλει το σπρέι πριν καθίσουμε στον κήπο το βράδυ.

Είναι καλό να... is a very common Greek pattern meaning It is good to..., It’s a good idea to..., or It’s good that... depending on context.

In this sentence, it introduces a general recommendation:

• Είναι καλό = It is good / It’s a good idea
• να έχουμε βάλει... = to have put / to have applied...

So the whole beginning means something like It’s a good idea to have applied...

Greek often uses είναι + adjective + να-clause where English might use an infinitive:

• Είναι εύκολο να το κάνεις. = It’s easy to do it.
• Είναι σημαντικό να φύγουμε νωρίς. = It’s important to leave early.

This is one of the most useful things to notice in the sentence.

• να βάλουμε = to put / to apply
• να έχουμε βάλει = to have put / to have applied

So να έχουμε βάλει shows that the action should already be completed before another moment in time.

Here, the idea is:

• first: apply the spray
• then: sit in the garden

That is why Greek uses the perfect form έχουμε βάλει after να.

Compare:

• Είναι καλό να βάλουμε το σπρέι πριν καθίσουμε...
  = It’s good to put on the spray before we sit down.

• Είναι καλό να έχουμε βάλει το σπρέι πριν καθίσουμε...
  = It’s good to have already put on the spray before we sit down.

The second version stresses the completed result more clearly.

Έχουμε βάλει is the perfect of βάζω.

It is formed with:

• έχω in the present
• plus the invariant participle-like form, here βάλει

So:

• βάζω = I put / I am putting
• έβαλα = I put (once, completed action; past)
• έχω βάλει = I have put

In your sentence, it appears inside a να-clause:

• να έχουμε βάλει

This corresponds closely to English to have put or that we have put.

Yes, βάζω basically means put, but like many common verbs, it has a wider range of uses.

With something like το σπρέι, βάζω often means:

• put on
• apply
• use

So να έχουμε βάλει το σπρέι means:

• to have put on the spray
• to have applied the spray

This is very natural Greek. Greek often uses a general verb like βάζω where English may prefer a more specific verb such as apply.

After πριν (before), Greek often uses the subjunctive verb directly, without να.

So both ideas are related to:

• πριν καθίσουμε = before we sit / before we sit down

In Modern Greek, omitting να after πριν is very common and natural.

You may also encounter:

• πριν να καθίσουμε

But πριν καθίσουμε is very standard and common, especially in everyday language.

Καθίσουμε is the subjunctive form of καθίζω / κάθομαι in the sense of sit down.

Here it refers to a single completed action in the future sequence:

1. apply the spray
2. sit down in the garden

So καθίσουμε is the right form for before we sit down.

This is not the same as describing an ongoing state like while we are sitting. It points to the moment of sitting down.

Because the sentence refers to a specific action that has not happened yet, after πριν.

• καθίσουμε = we sit down / we are to sit
• καθόμαστε = we sit / we are sitting as an ongoing or habitual action

After words like πριν, Greek usually uses a subjunctive form for a future or anticipated action:

• πριν φύγουμε = before we leave
• πριν φάμε = before we eat
• πριν καθίσουμε = before we sit down

So καθόμαστε would not fit the structure here.

Yes. It belongs to the κάθομαι / καθίζω family.

Greek verbs can have different stems in different forms, and this is one of those cases. Learners often notice:

• κάθομαι = I sit / I am sitting
• κάτσω = I sit down / I will sit down
• καθίσω or καθίσω/καθίσω-type forms exist in more formal or alternative usage depending on the verb family
• καθίσουμε = we sit down

In practice, Greek has a few related forms around this verb, and usage varies somewhat between formal and everyday speech. A learner will often also hear:

• πριν κάτσουμε

That is very common in spoken Greek.
πριν καθίσουμε sounds a bit more careful or formal.

Στον is the contraction of:

• σε = in / to / at
• τον = the (masculine accusative singular)

So:

• σε τον κήπο becomes στον κήπο

Greek normally uses σε + accusative to express location as well as movement toward a place.

So:

• στον κήπο = in the garden

Even though English uses a special preposition like in, Greek often uses σε for both in and to, depending on context.

Examples:

• στο σπίτι = in the house / at home
• στο σχολείο = at school / to school
• στον κήπο = in the garden

Because after σε, Modern Greek uses the accusative.

So:

• nominative: ο κήπος
• accusative: τον κήπο

And with σε + τον:

• σε τον κήπο → στον κήπο

This is normal Greek grammar. Modern Greek no longer has a separate case just for location, so the accusative is used after many prepositions, including σε.

Το βράδυ means in the evening or at night, depending on context.

In this sentence, it most naturally means:

• in the evening
• possibly at night

Greek often uses the article with time expressions:

• το πρωί = in the morning
• το μεσημέρι = at noon / midday
• το απόγευμα = in the afternoon
• το βράδυ = in the evening / at night

So the article το is completely normal here.

Σπρέι is a borrowed word from English (spray), and in Greek it is typically:

• neuter
• usually indeclinable in everyday use

So you get:

• το σπρέι = the spray

Its form usually stays the same:

• το σπρέι
• του σπρέι
• τα σπρέι

In this sentence, το σπρέι is the direct object of βάλει.

Yes, Greek word order is more flexible than English word order.

The version in your sentence is neutral and natural:

• να έχουμε βάλει το σπρέι πριν καθίσουμε στον κήπο το βράδυ

But Greek could move parts around for emphasis, for example:

• Είναι καλό πριν καθίσουμε στον κήπο το βράδυ να έχουμε βάλει το σπρέι.
• Είναι καλό να έχουμε βάλει πριν καθίσουμε το σπρέι.
  (possible, though less natural in this exact context)

So the original order is not the only possible one, but it is smooth and clear.

Yes, it is understandable and basically natural. It sounds a little careful or slightly formal because of καθίσουμε and the perfect να έχουμε βάλει.

In everyday speech, many Greeks might also say something a bit simpler, such as:

• Είναι καλό να βάλουμε το σπρέι πριν κάτσουμε στον κήπο το βράδυ.
• Καλό είναι να έχουμε βάλει το σπρέι πριν καθίσουμε στον κήπο το βράδυ.

These are just stylistic differences. Your sentence is perfectly good Greek.

It breaks down like this:

• Είναι καλό = It is good / It’s a good idea
• να έχουμε βάλει το σπρέι = to have applied the spray
• πριν καθίσουμε στον κήπο = before we sit down in the garden
• το βράδυ = in the evening / at night

So the full logic is:

It’s a good idea for us to have already applied the spray before sitting in the garden in the evening.

The key grammar points are:

1. είναι καλό + να-clause
2. perfect: να έχουμε βάλει
3. πριν + subjunctive: πριν καθίσουμε
4. σε + accusative: στον κήπο
5. time phrase with article: το βράδυ