Jag måste skala potatisen innan gästerna kommer.

Because after the modal verb måste (must / have to), Swedish normally uses the bare infinitive without att.

• Jag måste skala potatisen = I have to peel the potatoes
• Not: Jag måste att skala ...

This is similar to English, where we say I must peel, not I must to peel.

Common Swedish modal verbs that also work this way include:

• kan = can
• ska = will / am going to / should
• vill = want to
• får = may / am allowed to
• måste = must / have to

So måste + infinitive is the normal pattern.

Skala means to peel.

In this sentence, it means removing the skin from potatoes before cooking them.

A few useful related forms:

• att skala = to peel
• skalar = peels / am peeling / peel
• skalade = peeled
• har skalat = have peeled

So Jag måste skala potatisen means I need to peel the potatoes.

Potatisen is the definite form, literally the potato or, in context, the potatoes.

Swedish often uses the definite form when talking about something specific that both speaker and listener understand. Here, it means the potatoes being prepared for the guests.

Compare:

• skala potatis = peel potatoes / peel potato in a general sense
• skala potatisen = peel the potatoes, the specific potatoes we are talking about

So potatisen makes it sound more specific and natural in this context.

Because potatis is often used as a mass noun or collective noun in Swedish.

So potatisen can literally look singular, but in real usage it may refer to the potatoes as food or as a batch of potatoes being prepared.

This is very natural in Swedish. English often prefers the plural the potatoes, while Swedish may use potatisen for the whole amount involved.

So the form is not strange—it is just one of those places where Swedish and English organize the idea a bit differently.

Gästerna means the guests.

It is built from:

• gäst = guest
• gäster = guests
• gästerna = the guests

So this is the definite plural form.

That makes sense here because we are talking about specific guests who are expected to arrive.

Swedish often uses the present tense to talk about the future when the future event is clear from context.

So:

• gästerna kommer literally looks like the guests come
• but it means the guests are coming / the guests will come

Because innan (before) already places the action in a future relationship, Swedish does not need a special future form here.

This is similar to English in sentences like:

• I’ll do it before they arrive
• not usually before they will arrive

So innan gästerna kommer is completely natural Swedish.

Because innan introduces a subordinate clause, and Swedish word order in subordinate clauses is different from main clauses.

Main clause:

• Gästerna kommer snart. = The guests are coming soon.

Subordinate clause after innan:

• innan gästerna kommer = before the guests come

In Swedish, subordinate clauses normally keep subject + verb order, so gästerna kommer is correct.

This is an important pattern to learn:

• Jag stannar här eftersom jag är trött.
• Vi äter när han kommer.
• Jag måste skala potatisen innan gästerna kommer.

Innan means before and is commonly used before a clause.

Here it introduces a full clause:

• innan gästerna kommer = before the guests come

Före is more often used before a noun phrase:

• före middagen = before dinner
• före gästerna = before the guests

So in this sentence, innan is the natural choice because it is followed by a clause with a subject and verb.

A helpful rule of thumb:

• innan + clause
• före + noun

Yes, you can, and it changes the nuance slightly.

• skala potatisen = peel the potatoes, a specific batch of potatoes
• skala potatis = peel potatoes, more general activity / less specific

Both are possible, but potatisen sounds more like the speaker has particular potatoes in mind, which fits this situation very well.

So:

• Jag måste skala potatisen innan gästerna kommer = very natural if you mean the potatoes for the meal
• Jag måste skala potatis innan gästerna kommer = also possible, slightly more general

Not always.

In many cases, måste can mean either:

• must
• have to
• need to

In everyday English, I have to peel the potatoes often sounds more natural than I must peel the potatoes, but Swedish måste covers that idea very naturally.

So in this sentence, måste is best understood as a practical necessity, not necessarily a very formal or dramatic must.

A very natural English rendering would be:

• I have to peel the potatoes before the guests arrive.

That matches the Swedish well, even though Swedish uses:

• a definite form in potatisen
• present tense kommer for a future event

So when learning from this sentence, it helps to separate:

• the meaning
• the literal structure
• the most natural translation

The sentence has two parts:

1. Jag måste skala potatisen

   • Jag = subject
   • måste = modal verb
   • skala = infinitive
   • potatisen = object

2. innan gästerna kommer

   • innan = subordinating conjunction
   • gästerna = subject
   • kommer = verb

So the overall pattern is:

subject + modal verb + infinitive + object + subordinate clause

This is a very common and useful Swedish sentence pattern.