Što više olabaviš vijak, to lakše rastaviš deo.

It is a very common comparative pattern meaning the more ..., the ....

So:

• Što više olabaviš vijak, to lakše rastaviš deo.
• literally follows the logic The more you loosen the screw, the more easily you take the part apart.

A good way to recognize it is:

• što + comparative
• to + comparative

Examples of the same pattern:

• Što više učiš, to više znaš. = The more you study, the more you know.
• Što je hladnije, to je teže raditi. = The colder it is, the harder it is to work.

Here, što does not mean what. In this sentence it is part of the fixed correlative pattern.

Više means more, and here it modifies the verb olabaviš.

So više olabaviš means loosen more or loosen it to a greater degree.

This is adverbial use:

• više raditi = to work more
• više otvoriti = to open more
• više olabaviti = to loosen more

It does not mean many here. It means more in degree.

Because lakše is an adverb, not an adjective.

It modifies the verb rastaviš, so it means more easily.

Compare:

• lak deo = an easy/light part depending on context → adjective
• lakše rastaviš = you dismantle it more easily → adverb

A useful rule:

• if the word describes a noun, you usually need an adjective
• if it describes a verb, you usually need an adverb

Here the sentence is talking about how you dismantle the part, so lakše is correct.

They are present-tense forms, but the sentence expresses a general relationship, not just something happening right now.

Serbian often uses the present tense for:

• general truths
• instructions
• cause-and-effect statements
• habitual or repeatable situations

So this sentence means something like a general rule:

• whenever you loosen the screw more, you dismantle the part more easily

Also, these are 2nd person singular forms:

• olabaviš
• rastaviš

That does not necessarily mean one specific you. It can be generic you, just like in English:

• The more you practice, the better you get.

Because Serbian usually does not need subject pronouns when the verb ending already shows the subject.

The ending -š tells you it is you singular:

• olabaviš = you loosen
• rastaviš = you dismantle

So adding ti is normally unnecessary unless you want emphasis or contrast.

For example:

• Ti olabaviš vijak, a ja držim deo. = You loosen the screw, and I hold the part.

In your sentence, no emphasis is needed, so the pronoun is omitted.

They are in the accusative, because they are the direct objects of the verbs:

• olabaviš vijak = loosen the screw
• rastaviš deo = dismantle the part

However, for masculine inanimate nouns, the accusative is often identical to the nominative. That is why the forms look unchanged:

• nominative: vijak

• accusative: vijak

• nominative: deo
• accusative: deo

If the noun were masculine animate, you would usually see a different accusative form.

Here they are understood as perfective forms:

• olabaviti = to loosen up / make looser
• rastaviti = to take apart / dismantle

That gives the sentence a sense of achieving a result:

• first you loosen the screw
• then the part becomes easier to dismantle

Perfective verbs are very natural when the speaker is thinking in terms of completed actions and their result.

If you used imperfective verbs, the focus would shift more toward the ongoing process or repeated action, and the sentence would sound different in nuance.

The overall pattern is fairly fixed, but there is some flexibility inside it.

The most natural structure is:

• Što + comparative + first clause, to + comparative + second clause

So your sentence is very natural as:

• Što više olabaviš vijak, to lakše rastaviš deo.

You can move some elements around for emphasis, but it may sound more marked or less neutral. For learners, it is best to keep this standard pattern.

Also, the comma is important because the sentence has two linked parts.

It is understandable and natural, but a learner may notice a bit of mixed flavor.

Points to notice:

• deo is the common Ekavian Serbian form
• in Ijekavian varieties, you would often see dio
• vijak is perfectly understandable, but in everyday Serbian many speakers would also say šraf or sometimes zavrtanj, depending on context and register

So the sentence is fine, but it may sound a little more technical or cross-standard than a purely everyday colloquial Serbian sentence.

For example, a more everyday Serbian variant might be:

• Što više olabaviš šraf, to lakše rastaviš deo.

Sometimes in casual speech people may shorten this kind of pattern, but in standard, clear Serbian it is best to keep to.

So:

• Što više olabaviš vijak, to lakše rastaviš deo.

is the full and safest form.

The to helps mark the second half of the correlation:

• the more ... , the more/the easier ...

For learners, keeping both parts — što and to — is the best habit.