Dacă farul ar merge, șoferul ar pleca.

This is a hypothetical / unreal conditional, very similar to the English second conditional:

• Dacă ... ar merge = If ... were working / would work
• ... ar pleca = ... would leave

It describes a situation that is not being presented as real, but as imagined, possible, or contrary to the current facts.

So the pattern is:

• Dacă + conditional
• conditional

In this sentence, both verbs are in the conditional mood.

Because Romanian often uses the conditional mood in both parts of this kind of hypothetical sentence.

So:

• ar merge = would work
• ar pleca = would leave

This is different from English, where we usually say:

• If the headlight worked, the driver would leave

English uses a past form (worked) in the if-clause, but Romanian commonly uses the conditional there too:

• Dacă farul ar merge...

That is a normal thing for learners to notice, because it does not match English word-for-word.

Ar merge is the 3rd person singular conditional present of a merge.

Romanian conditional present is built with a conditional auxiliary plus the infinitive:

• aș merge = I would go / I would work
• ai merge = you would go / work
• ar merge = he/she/it would go / work
• am merge = we would go / work
• ați merge = you all would go / work
• ar merge = they would go / work

In your sentence:

• farul is singular, so you get ar merge
• șoferul is also singular, so you get ar pleca

Yes, a merge very often means to go, but it also has another very common meaning:

• to function
• to work (for machines, devices, systems, lights, etc.)

So in this sentence, farul ar merge does not mean the headlight would go. It means:

• the headlight would work
• the headlight would function

This use of a merge is extremely common in Romanian:

• Mașina nu merge. = The car isn’t working / won’t run.
• Telefonul merge. = The phone works.
• Farul merge. = The headlight works.

Yes. Far can mean:

• headlight
• lighthouse

But in this sentence, because of șoferul (the driver), the natural meaning is the headlight.

So:

• farul here = the headlight

Romanian relies on context a lot. If the sentence were about the sea or ships, farul would probably mean the lighthouse.

Because Romanian usually attaches the definite article to the end of the noun.

So:

• far = a headlight / headlight
• farul = the headlight

and

• șofer = driver
• șoferul = the driver

This is one of the big differences from English. Instead of a separate word like the, Romanian often adds it to the noun itself.

A few more examples:

• băiat = boy

• băiatul = the boy

• om = person / man
• omul = the person / the man

Yes, in this sentence dacă means if.

It introduces a condition:

• Dacă farul ar merge = If the headlight worked

A useful note: dacă can also introduce whether / if in indirect questions:

• Nu știu dacă vine. = I don’t know if/whether he is coming.

But in your sentence it is clearly the conditional if.

Because the sentence begins with a subordinate clause introduced by dacă:

• Dacă farul ar merge,
• șoferul ar pleca.

Romanian normally uses a comma to separate this kind of introductory conditional clause from the main clause.

If the order were reversed, you would usually not need the comma in the same way:

• Șoferul ar pleca dacă farul ar merge.

Both word orders are possible.

Yes. That is perfectly natural.

Both are correct:

• Dacă farul ar merge, șoferul ar pleca.
• Șoferul ar pleca dacă farul ar merge.

The difference is mostly one of focus and style:

• Starting with Dacă... emphasizes the condition.
• Starting with Șoferul ar pleca... emphasizes the result.

Yes, you can, but it is optional.

For example:

• Dacă farul ar merge, atunci șoferul ar pleca.

This is understandable and grammatical, but often Romanian simply leaves atunci out:

• Dacă farul ar merge, șoferul ar pleca.

That shorter version is very natural.

Usually, yes. A pleca means to leave or to depart.

So:

• șoferul ar pleca = the driver would leave

Depending on context, it could mean:

• leave the place
• set off
• go away
• depart

So it is a broad everyday verb, much like English leave.

Yes, absolutely.

You could say:

• Dacă farul ar funcționa, șoferul ar pleca.

That means essentially the same thing:

• If the headlight were functioning, the driver would leave.

The difference is style:

• a merge is more common and more colloquial in everyday Romanian for machines and devices
• a funcționa is more explicit and a bit more formal or technical

So in normal speech, farul merge / nu merge is very natural.

It is mainly about a hypothetical present or future situation.

It suggests something like:

• right now the headlight is not working, or
• we are imagining the case where it would work

Then:

• the driver would leave

So this is not normally understood as a past event. It is a present/future hypothetical.

A few quick pronunciation notes:

• ș = sh as in ship
• ă = a short central vowel, something like the a in sofa
• că sounds roughly like kuh
• ce / ci can sound like che / chi, but that does not apply here

So approximately:

• Dacă ≈ DA-kuh
• șoferul ≈ SHO-fe-rul
• farul ≈ FA-rul
• pleca ≈ ple-KA
• merge ≈ MER-je / MER-zhe depending on how you approximate it in English

The g in merge is like the sound in measure, not like the hard g in go.

Yes, it is possible.

Even though a car normally has two headlights, singular farul can still make sense if:

• you are talking about one specific headlight
• one of them matters in the situation
• the example sentence is just illustrating grammar

If you wanted the plural, you could say:

• Dacă farurile ar merge, șoferul ar pleca.
  = If the headlights worked, the driver would leave.

So the singular is not wrong; it just refers to one headlight.

A very useful pattern is:

• Dacă + noun + ar + infinitive, noun + ar + infinitive.

For example:

• Dacă mașina ar merge, am pleca.
  = If the car worked, we would leave.

• Dacă ar veni, l-aș vedea.
  = If he came, I would see him.

From your sentence, the main thing to remember is:

• dacă = if
• ar + infinitive = a common way to form the conditional
• Romanian can use this conditional pattern in both the if-clause and the result clause in hypothetical statements