Olabavi vijak pre nego što rastaviš deo.

Olabavi is the imperative singular form, used to give a command to one person.

• Infinitive: olabaviti = to loosen
• Imperative: olabavi! = loosen!

So in this sentence, olabavi vijak means loosen the screw.

It means loosen in the sense of make less tight.

That is slightly different from verbs meaning unscrew completely or remove by turning.
So olabavi vijak usually suggests:

• make the screw looser first
• not necessarily take it all the way out

That fits well with the rest of the sentence: first loosen it, then take the part apart.

Serbian often drops subject pronouns when they are already clear from the verb ending.

Here:

• olabavi = command to you singular
• rastaviš = you disassemble / take apart

Because the verb forms already show the subject, ti is unnecessary.

You could say Ti olabavi vijak..., but that usually sounds more emphatic, like you loosen the screw...

Because the second clause is not another command by itself. It is part of the expression pre nego što = before.

So:

• Olabavi = the main command
• pre nego što rastaviš deo = before you take apart the part

Here rastaviš is a present-tense form used after pre nego što, even though English often thinks of the action as future relative to the command.

In Serbian, after pre nego što, it is normal to use a present form like rastaviš.

Literally, it is structured like:

• before you disassemble the part

This is very natural in Serbian. It does not mean the action is happening right now. In this context, it refers to the action that is expected to happen later.

So pre nego što rastaviš deo is the normal way to say before you take the part apart.

Both are from perfective verbs:

• olabaviti = to loosen up / loosen completely as a completed action
• rastaviti = to take apart / disassemble as a completed action

That matters because the sentence is talking about two single completed steps:

1. loosen the screw
2. then disassemble the part

Perfective verbs are very common when giving instructions, especially for step-by-step actions.

Because vijak is the direct object, so it is in the accusative case.
For masculine inanimate nouns, the accusative singular is usually the same as the nominative.

So:

• nominative: vijak = a screw / the screw
• accusative: vijak = a screw / the screw as the object

That is why you see olabavi vijak.

For the same reason as vijak: deo is also a direct object, so it is in the accusative singular.

And again, because it is a masculine inanimate noun, the accusative looks the same as the nominative:

• nominative: deo = part
• accusative: deo = part as the object

So rastaviš deo is grammatically regular.

Correct. Serbian does not have articles like a and the.

So:

• vijak can mean a screw or the screw
• deo can mean a part or the part

The exact meaning depends on context. In an instruction like this, English often uses the:

• Loosen the screw before you disassemble the part.

But Serbian simply uses the noun without an article.

It means before or more literally before than that in structure, though you should learn it as one set phrase:

• pre nego što = before

Examples:

• Operi ruke pre nego što jedeš.
  Wash your hands before you eat.

• Proveri kabl pre nego što uključiš uređaj.
  Check the cable before you switch on the device.

It is a very common way to introduce an action that happens later than the main one.

Yes. Serbian word order is fairly flexible.

The original order:

• Olabavi vijak pre nego što rastaviš deo.

A different but still natural order would be:

• Pre nego što rastaviš deo, olabavi vijak.

Both mean the same thing. The original version puts the command first, which is very natural in instructions.

A simple pronunciation guide:

• Olabavi ≈ oh-lah-BAH-vee
• vijak ≈ VEE-yahk
• pre nego što ≈ preh NEH-goh shtoh
• rastaviš ≈ rah-STAH-veesh
• deo ≈ DEH-oh

So the whole sentence is roughly:

oh-lah-BAH-vee VEE-yahk preh NEH-goh shtoh rah-STAH-veesh DEH-oh

The š sound is like sh in shoe.

Yes, deo is the standard Serbian Ekavian form.

In some other closely related standards, you may see:

• dio instead of deo

So if you are learning Serbian, deo is exactly what you should expect in standard Ekavian Serbian.