Drži se za mene dok idemo preko mosta.

Drži se is the informal singular imperative of držati se.

• držati = to hold, keep
• držati se = to hold on, cling, keep oneself attached

So in this sentence, drži se means hold on.

The se is a reflexive particle. In Croatian, many verbs change meaning when they are used with se. Here, držati and držati se are not quite the same:

• Drži me. = Hold me.
• Drži se za mene. = Hold on to me.

So se is essential here.

Because Croatian uses the pattern držati se za + accusative for hold on to someone/something.

So:

• za mene = onto me / to me
• za tebe = onto you
• za ogradu = onto the fence/railing

If you said Drži me, that would mean Hold me, not Hold on to me.

So the difference is:

• Drži me. = Hold me.
• Drži se za mene. = Hold on to me.

Because za here requires the accusative case, and the accusative form of ja is mene (or sometimes me, depending on context).

Relevant forms are:

• ja = I
• mene / me = me

After a preposition like za, Croatian normally uses the full/stressed form:

• za mene = for me / onto me

You would not say za me in this kind of standard sentence.

Drži is the 2nd person singular imperative, so it is used when speaking to one person informally.

Examples:

• Drži se za mene. = Hold on to me. (to one person, informal)
• Držite se za mene. = Hold on to me. (to more than one person, or to one person formally/politely)

So this sentence sounds like you are speaking to one person you know well, such as a child, friend, partner, or family member.

Dok means while or as.

Idemo is the 1st person plural present tense of ići = to go.

So dok idemo means:

• while we are going
• as we go

Croatian often uses the present tense after dok when two actions are happening at the same time.

So:

• Drži se za mene dok idemo preko mosta. = Hold on to me while we’re going across the bridge.

English often prefers while we’re going, but Croatian simply uses the present: idemo.

Both are possible, but they emphasize slightly different things.

• idemo preko mosta = we are going across the bridge
• prelazimo most = we are crossing the bridge

In this sentence, idemo preko mosta sounds natural and conversational. It focuses on the movement in general.

A very similar alternative would be:

• Drži se za mene dok prelazimo most.

That also works and may sound a bit more directly like while we’re crossing the bridge.

Because the preposition preko takes the genitive case.

So:

• most = bridge (nominative)
• mosta = of the bridge / bridge (genitive form after certain prepositions)

That is why you get:

• preko mosta = across the bridge / over the bridge

Other examples:

• preko ceste = across the road
• preko rijeke = across the river

In this sentence, it most naturally means across the bridge.

Literally, preko often corresponds to over / across. The exact English translation depends on context.

Here, since you are moving from one side to the other using the bridge, English usually says:

• across the bridge

So although preko can sometimes feel like over, the best natural meaning here is across.

In this specific meaning, za is the normal choice.

• držati se za nekoga/nešto = to hold on to someone/something

So:

• Drži se za mene. = Hold on to me.

Without za, the meaning changes or becomes less natural in this context. For a learner, it is best to remember the full pattern:

• držati se za + accusative

Here are the main forms:

• drži → from držati se = to hold on
• se → reflexive particle
• za = for, by, onto, behind; here onto
• mene → accusative form of ja = me
• dok = while
• idemo → from ići = to go
• preko = across, over
• mosta → genitive form of most = bridge

This is useful because Croatian sentences often contain words that are not in their dictionary form.

The given word order is natural, but Croatian word order is fairly flexible.

Standard, natural version:

• Drži se za mene dok idemo preko mosta.

Possible variations include:

• Dok idemo preko mosta, drži se za mene.
• Drži se za mene dok preko mosta idemo. (less neutral, more marked)

Croatian can move parts around for emphasis, but the original sentence is the most straightforward and natural for everyday use.

You would change the imperative drži to držite:

• Držite se za mene dok idemo preko mosta.

This can mean:

• Hold on to me while we go across the bridge. (to several people)
• or a formal/polite you to one person

Everything else stays the same.