Muszę obrać ziemniaki przed obiadem.

Muszę means I must or I have to.

It is the 1st person singular form of the verb musieć (to have to / must). So:

• muszę = I have to
• musisz = you have to
• musi = he/she/it has to

In this sentence, muszę shows necessity or obligation.

Polish often leaves out subject pronouns when they are already clear from the verb form.

Since muszę already means I have to, adding ja is usually unnecessary. So:

• Muszę obrać ziemniaki = I have to peel the potatoes
• Ja muszę obrać ziemniaki also works, but ja adds emphasis, like I have to peel them.

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

• obrać = perfective
• obierać = imperfective

Here, obrać is used because the speaker means a completed action: the potatoes need to end up peeled before the meal.

So:

• Muszę obrać ziemniaki = I need to peel them completely
• Muszę obierać ziemniaki would sound more like focusing on the process, repeated action, or being in the middle of peeling

In this sentence, perfective obrać is the natural choice.

In Polish, the infinitive does not use a separate word like English to.

So:

• English: to peel
• Polish: obrać

After verbs like muszę, Polish simply uses the infinitive directly:

• muszę iść = I have to go
• muszę zrobić = I have to do/make
• muszę obrać = I have to peel

Ziemniaki is in the accusative plural, because it is the direct object of obrać.

The dictionary form of the singular noun is ziemniak (potato). The plural is ziemniaki (potatoes).

For this type of noun, the accusative plural looks the same as the nominative plural, so you see:

• nominative plural: ziemniaki
• accusative plural: ziemniaki

That is why the form does not change here.

Because przed usually requires the instrumental case when it means before or in front of.

The noun obiad changes like this:

• nominative: obiad
• instrumental: obiadem

So:

• przed obiadem = before lunch / before dinner

This is a very common pattern in Polish:

• przed szkołą = before/in front of the school
• przed pracą = before work
• przed obiadem = before lunch/dinner

It depends on context and on the family or region.

In Polish, obiad usually means the main meal of the day, often eaten in the afternoon. In English, that may be translated as:

• lunch in some contexts
• dinner in others

So both translations can be possible, depending on the situation. The important idea is that it is the meal called obiad.

Yes. Polish word order is more flexible than English word order.

The neutral version is:

• Muszę obrać ziemniaki przed obiadem.

But you could also say:

• Przed obiadem muszę obrać ziemniaki.
• Ziemniaki muszę obrać przed obiadem.

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

• Przed obiadem... emphasizes the time
• Ziemniaki... emphasizes what has to be peeled

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

Yes. Ziemniaki means potatoes, plural.

The singular is ziemniak = potato.

So:

• Muszę obrać ziemniak = I have to peel one potato
• Muszę obrać ziemniaki = I have to peel potatoes

In real life, the plural is very common because people usually peel more than one potato at a time.