Předchozí majitel opravil motor.

Because of case and verb agreement.

• majitel is in the nominative case, which is the usual case for the subject.
• motor is in the accusative case, which is the usual case for the direct object.

In this sentence, motor looks the same in nominative and accusative because it is a masculine inanimate noun. That is very common in Czech.

So the structure is:

• Předchozí majitel = the subject, the previous owner
• opravil = repaired/fixed
• motor = the object, the engine/motor

This is a question of aspect, which is very important in Czech.

• opravit → perfective: to repair/fix something successfully, as a completed action
• opravovat → imperfective: to repair/fix, in progress, repeatedly, or without focusing on completion

So:

• opravil motor = he repaired/fixed the engine; the action is seen as completed
• opravoval motor = he was repairing the engine / he used to repair the engine / the completion is not the main point

In your sentence, opravil tells us the engine got repaired.

In Czech, past tense is often formed with a past participle-like form ending in -l plus forms of být (to be).

Here, opravil is the masculine singular past form of opravit.

In the 3rd person, Czech usually leaves out the auxiliary:

• opravil jsem = I repaired
• opravil jsi = you repaired
• opravil = he repaired
• opravila = she repaired
• opravili = they repaired (masculine animate or mixed group)

So opravil by itself already means he repaired, and with majitel it becomes the owner repaired.

Yes, předchozí is an adjective meaning previous or preceding, and it agrees with the noun in gender, number, and case.

Here it modifies majitel, which is:

• masculine animate
• singular
• nominative

So we get předchozí majitel.

A useful thing to know is that adjectives ending in -í often have the same form in several nominative forms, so předchozí may look unchanged more often than some other adjectives. But it does decline in other cases, for example:

• bez předchozího majitele = without the previous owner

Předchozí means previous, preceding, or sometimes former, depending on context.

In this sentence, předchozí majitel most naturally means:

• the previous owner
• possibly the former owner

It refers to the person who owned it before the current owner.

Yes. Czech word order is fairly flexible because case endings help show grammatical roles.

The neutral order here is:

• Předchozí majitel opravil motor.

But you could also say:

• Motor opravil předchozí majitel.
• Předchozí majitel motor opravil.

These versions still mean roughly the same thing, but the focus changes:

• starting with motor emphasizes the engine
• putting opravil later can emphasize the fact that it was repaired

So the original sentence is a normal, neutral way to say it.

Because the subject is already stated: předchozí majitel.

Also, the verb form opravil already matches a masculine singular subject in the past tense. Czech often leaves pronouns out unless they are needed for emphasis or contrast.

So unlike English, Czech does not need to say something like He repaired it if the noun subject is already present.

You would change both the noun and the past-tense verb form:

• Předchozí majitelka opravila motor.

Here:

• majitelka = female owner
• opravila = feminine singular past tense

So Czech past tense agrees with the gender of the subject in the singular.

A rough learner-friendly guide is:

• Předchozí ≈ PRZHET-kho-zee
• majitel ≈ MY-yi-tel
• opravil ≈ O-pra-vil
• motor ≈ MO-tor

A few important points:

• Czech stress is usually on the first syllable of each word.
• ch is pronounced like the ch in German Bach or Scottish loch, not like English ch in chair.
• ř is a famous Czech sound with no exact English equivalent. At first, an approximation is fine.
• í is a long vowel, so -zí is pronounced longer than short i.

You do not need perfect ř right away to be understood.