A cég a javításon dolgozik.

• a = the
• cég = company, firm
• a javításon = on the repair, on the fixing/repair work
• dolgozik = works, is working

So the sentence is built very literally as The company is working on the repair.

Because Hungarian uses the definite article a / az before each definite noun, just as English can use the more than once:

• a cég = the company
• a javításon = on the repair

A useful thing to notice is that the case ending goes on the noun, not on the article:

• a javítás = the repair
• a javításon = on the repair

The article stays a.

The basic form is javítás, which means repair or repairing.

It is formed from the verb javít = repair, fix plus the noun-forming suffix -ás/-és:

• javít = to repair
• javítás = repair / repairing

Then Hungarian adds the ending -on:

• javítás → javításon

So javításon literally means on a/the repair.

Because the verb dolgozik often uses the superessive case (-on/-en/-ön) to express working on something.

A very common pattern is:

• dolgozik valamin = to work on something

So:

• a javításon dolgozik = is working on the repair

This is one of those verb + case combinations that you mostly have to learn as a set. English says work on, and Hungarian also uses a form that often corresponds to on.

No, that would not be correct here.

a javítást is accusative, which is usually used for a direct object. But dolgozik does not take javítás as a direct object in this meaning. Hungarian says:

• dolgozik valamin = works on something

not

• dolgozik valamit for this idea

So the natural form is:

• A cég a javításon dolgozik.

Because the dictionary form and 3rd person singular present form of this verb is dolgozik.

Some forms are:

• én dolgozom / dolgozok = I work
• te dolgozol = you work
• ő dolgozik = he/she/it works

So with a cég = the company (3rd person singular), the correct form is dolgozik.

It can mean either, depending on context.

Hungarian does not have a separate progressive form like English is working. The plain present tense can cover both:

• habitual: works
• ongoing right now: is working

In this sentence, because of a javításon and the overall context, the most natural English translation is usually is working on the repair.

Because cég is a singular noun meaning company or firm, just like English the company is grammatically singular:

• A cég dolgozik... = The company is working...

Even if many employees are actually doing the work, Hungarian still treats cég as singular here.

Not completely, but this order is very natural.

• A cég a javításon dolgozik. = neutral, natural statement

You may also hear other orders, but they change emphasis:

• A javításon dolgozik a cég.
  This puts more attention on what the company is working on.

Hungarian often places the element most closely connected to the verb right before the verb, so a javításon dolgozik feels very normal.

Because languages do not always organize ideas with the same prepositions or cases.

In English, work on is natural, but on the repair can sound slightly stiff or unusual depending on context. In Hungarian, however, valamin dolgozik is the normal pattern.

So you should not try to match the wording too literally. The important thing is the Hungarian structure:

• dolgozik valamin = works on something

Yes. A few related possibilities are:

• A cég javítja a hibát. = The company is repairing the fault/problem.
  This is more direct and uses a verb with a direct object.

• A cég a hiba javításán dolgozik. = The company is working on fixing the fault/problem.
  This is more explicit about what is being repaired.

Your original sentence, A cég a javításon dolgozik, emphasizes that the company is engaged in the repair work as an ongoing task or project.