Learn Hardcore Swedish: Hennes pappa stannar hemma och lagar middag.

In Swedish, a possessive determiner (min, din, hans, hennes, vår, er, deras, etc.) blocks the definite suffix. You use the base (indefinite) form of the noun: hennes pappa, not hennes pappan.

Compare: min bil (not min bilen), deras lägenhet (not deras lägenheten).

Why not sin pappa here?

sin/sitt/sina is the reflexive possessive and refers back to the subject of the same clause. It is not used inside the subject noun phrase itself, so Sin pappa stannar hemma is ungrammatical. You must use a non‑reflexive form like hans/hennes: Hennes pappa stannar hemma ...
Correct uses of reflexive in other positions:

Hon stannar hemma med sin pappa.
Pappan stannar hemma och lagar sin middag.

What’s the difference between stannar hemma and är hemma?

stannar hemma = stays at home (chooses not to go out, remains there). It’s about the action/decision.
är hemma = is at home (states location).
Examples: Idag stannar jag hemma, but Jag är hemma nu.

Why hemma and not hem? Do I need a preposition?

hemma means “at home” (location) and takes no preposition: stannar hemma, är hemma.
hem is direction (“home/going home”): gå hem, åka hem, kom hem.
Don’t say stannar hem or i hemma.

Why is there no article before middag?

Meals typically appear without an article when used generically/idiomatically: laga middag, äta frukost, äta lunch.
Use an article/definite form when you mean a specific meal:

Han lagar middagen (the dinner we’ve mentioned).
Hon lagar en middag för tio personer (one dinner as an event).

Can I say gör middag or göra mat?

The idiomatic verb is laga for cooking:

Natural: laga middag, laga mat.
Colloquial: fixa middag (informal).
Unnatural: göra middag, göra mat (avoid).

Why do both verbs end in -ar (stannar, lagar)? What tense is this?

They’re present tense forms of regular Group 1 verbs. Swedish present covers both English simple and progressive meanings:

Han lagar middag (nu/ofta).
To stress ongoing action, you can say: Han håller på att laga middag. For future: Han ska/kommer att laga middag (context often lets present imply future).

Do I need to repeat the subject before the second verb?

No. With och, Swedish freely coordinates two verb phrases that share the same subject: Hennes pappa stannar hemma och lagar middag. You only repeat a subject if it changes or for emphasis/clarity in longer sentences.

Where does inte (not) go in this sentence?

Place inte after the finite verb in each clause:

Negating the first verb: Hennes pappa stannar inte hemma och lagar middag.
Negating the second verb: Hennes pappa stannar hemma och lagar inte middag.

Do I need a comma before och here?

No. Swedish normally does not use a comma before och when coordinating two verbs with the same subject. A comma may appear before och when linking two full main clauses, but it isn’t needed in this sentence.

If I add a time word like ikväll, where does it go?

Common options:

At the end: Hennes pappa stannar hemma ikväll och lagar middag.
In the first position (V2 kicks in): Ikväll stannar hennes pappa hemma och lagar middag.
Note the finite verb stannar stays in second position in main clauses.

Is pappa the same as far?

Both mean “father,” but:

pappa = dad (neutral, everyday).
far = father (more formal/literary or in set phrases: farföräldrar, farbror).

Does laga also mean “repair”? Why isn’t that confusing?

Yes, laga can mean both “cook” and “repair.” The object decides the meaning:

Cooking: laga middag, laga mat, laga soppa.
Repairing: laga cykeln, laga datorn, laga hålet.
With middag, it always means “cook.”