Αν τρυπήσεις τον τοίχο, πρέπει μετά να βιδώνεις προσεκτικά και να μην βιάζεσαι.

Τρυπήσεις is the 2nd person singular perfective non-past form of τρυπάω / τρυπώ.

In this sentence, after αν, it means something like if you drill / if you make a hole. It refers to one complete action, not an ongoing process.

For an English speaker, it may look like a future or subjunctive form. In practical terms, after αν, Greek often uses this form for a future possible condition.

Because αν and να do different jobs, and in this kind of conditional sentence Greek uses αν + non-past form, not αν να.

So:

• Αν τρυπήσεις... = If you drill / if you make a hole...

But:

• να τρυπήσεις would be used in a different structure, such as purpose, desire, instruction, or necessity.

A simple rule for learners is:

• αν introduces a condition
• να introduces a subjunctive clause after verbs like πρέπει, θέλω, μπορώ, etc.

Because τον τοίχο is the direct object of the verb τρυπήσεις.

You are drilling the wall, so the wall receives the action. In Greek, direct objects usually go in the accusative case.

So:

• ο τοίχος = the wall as subject
• τον τοίχο = the wall as object

That is why the article changes from ο to τον, and τοίχος becomes τοίχο.

Modern Greek generally does not use the infinitive the way English does.

So where English says:

• you must screw carefully
• you should not rush

Greek usually says:

• πρέπει να βιδώνεις
• να μην βιάζεσαι

In other words, Greek uses να + finite verb where English often uses an infinitive.

This is one of the biggest structural differences between English and Greek.

This is about aspect, which is very important in Greek.

• βιδώνεις = imperfective: focuses on the process, manner, or ongoing action
• βιδώσεις = perfective: focuses on the action as a whole or its completion

In this sentence, βιδώνεις προσεκτικά and να μην βιάζεσαι both focus on how you do it, not just on finishing it. So the imperfective βιδώνεις is natural here.

Very roughly:

• να βιδώνεις προσεκτικά = to be screwing it in carefully / to screw carefully
• να βιδώσεις = to screw it in / to get it screwed in

Both can be possible in different contexts, but this sentence emphasizes careful, unhurried process.

Because Greek normally introduces each new subjunctive verb with its own να, especially when the second part has its own idea or its own negation.

So:

• πρέπει μετά να βιδώνεις προσεκτικά και να μην βιάζεσαι

sounds natural and clear.

The second να helps mark μην βιάζεσαι as another verb phrase dependent on πρέπει.

For an English speaker, it may feel repetitive, but in Greek it is very normal.

Because μη(ν) is used to negate subjunctive and non-indicative forms, while δεν negates the indicative.

Here, βιάζεσαι is inside a να clause:

• να μην βιάζεσαι

So the correct negative is μην.

Compare:

• Δεν βιάζεσαι. = You are not in a hurry.
  Indicative statement

• Να μην βιάζεσαι. = Don’t rush / You shouldn’t rush.
  Subjunctive-type clause

That distinction is very important in Greek.

Here βιάζεσαι means to rush, to be in a hurry, or to do something hastily.

So να μην βιάζεσαι means:

• don’t rush
• don’t be in a hurry
• take your time

It does not mean simply to be fast in a neutral sense. It has the idea of acting too quickly or impatiently.

It looks passive because it uses middle/passive endings, but the verb βιάζομαι is one of many Greek verbs that have middle/passive form with active meaning.

So although βιάζεσαι looks like you are being hurried, in normal usage it means:

• you rush
• you are in a hurry

This is something English speakers often need to get used to: in Greek, some verbs are deponent-like, meaning their form looks non-active even though their meaning is active.

Grammatically, yes: it is 2nd person singular throughout:

• τρυπήσεις
• βιδώνεις
• βιάζεσαι

But it can also be understood as a generic you, just like in English:

• If you drill the wall, you must then screw carefully and not rush.

So it does not have to refer to one specific person. It can mean anyone doing this.

If you wanted to address more than one person directly, Greek would use plural forms instead.

Μετά here means afterwards, then, or after that.

So:

• πρέπει μετά να βιδώνεις προσεκτικά
  means
• you must then / afterwards screw carefully

Its position is fairly flexible. Greek often moves adverbs around for rhythm or emphasis. For example, these are all possible with slightly different flow:

• Πρέπει μετά να βιδώνεις...
• Μετά πρέπει να βιδώνεις...
• Πρέπει να βιδώνεις μετά...

The version in your sentence is very natural and places μετά neatly between πρέπει and the να clause.

It sounds more like a general instruction or practical advice.

That feeling comes from the combination of:

• Αν
  • conditional situation
• πρέπει = you must / should
• imperfective forms like βιδώνεις and βιάζεσαι, which emphasize process and manner

So the sentence is not just about one isolated event. It sounds like the kind of thing someone says when explaining the proper way to do this task:

• If you drill the wall, then you need to screw carefully and not rush.

That instructional tone is very natural in Greek.