Am Ende des Abends frieren wir den Rest ein und decken die Schüssel mit Alufolie ab.

On its own, frieren usually means to be cold:

• Ich friere. = I’m cold.

But here the verb is actually einfrieren, which is a separable verb meaning to freeze or to freeze something for later:

• Wir frieren den Rest ein. = We freeze the rest.

So the meaning changes because of the prefix ein-.

Because einfrieren is a separable verb. In a normal main clause, the conjugated part goes in the usual verb position, and the prefix moves to the end:

• Wir frieren den Rest ein.

Compare:

• infinitive: einfrieren
• main clause: wir frieren ... ein
• with modal: Wir wollen den Rest einfrieren.

This is very common in German with verbs like aufmachen, mitbringen, abdecken, einkaufen, etc.

Because den Rest is the direct object of einfrieren, so it is in the accusative case.

• nominative: der Rest
• accusative: den Rest

Here, wir is the subject, and den Rest is the thing being frozen.

It literally means the rest, but in this context it naturally means the leftovers or what’s left of the food.

So:

• den Rest einfrieren often means freeze the leftovers

German often uses der Rest where English might prefer the rest or the leftovers, depending on context.

For the same reason as einfrieren: abdecken is also a separable verb.

• infinitive: abdecken
• main clause: decken ... ab

So:

• Wir decken die Schüssel mit Alufolie ab.

means:

• We cover the bowl with aluminum foil.

Because die Schüssel is the direct object of abdecken: it is the thing being covered.

In this sentence, die Schüssel happens to look the same in nominative and accusative because it is feminine:

• nominative: die Schüssel
• accusative: die Schüssel

So the form does not change, but the function does.

Mit always takes the dative case.

So the phrase mit Alufolie means with aluminum foil.

Here Alufolie has no visible article, so you do not see a case ending. If there were an article, it would show the dative more clearly:

• mit der Alufolie = with the aluminum foil

In your sentence, mit Alufolie is perfectly natural and means using aluminum foil.

Because German often omits the article with materials or substances when speaking generally:

• mit Alufolie
• mit Wasser
• mit Zucker

So mit Alufolie means with aluminum foil in a general sense. If you mean specific foil already mentioned, you could say:

• mit der Alufolie

But in this sentence, no article is the most natural choice.

This phrase contains two useful pieces of grammar:

1. am = contraction of an dem
2. des Abends is genitive

So literally it is something like:

• at the end of the evening

Breakdown:

• das Ende = the end
• am Ende = at the end
• des Abends = of the evening

This is a very common pattern in German:

• am Anfang des Tages = at the beginning of the day
• am Ende der Woche = at the end of the week

Yes, grammatically that is fine, but it means at the end of the day, not specifically at the end of the evening.

So the choice depends on the situation:

• Am Ende des Abends = at the end of the evening
• Am Ende des Tages = at the end of the day

If you are talking about food after dinner or after guests leave, des Abends makes good sense.

German can omit the subject in the second clause when the subject is clearly the same:

• ... frieren wir den Rest ein und decken die Schüssel mit Alufolie ab.

This is similar to English:

• We freeze the rest and cover the bowl with foil.

You could also repeat it:

• ... frieren wir den Rest ein und wir decken die Schüssel mit Alufolie ab.

But that sounds less smooth unless you want extra emphasis.

Because when a sentence begins with a time expression or another element, German still keeps the conjugated verb in second position.

So:

• Wir frieren am Ende des Abends den Rest ein.
• Am Ende des Abends frieren wir den Rest ein.

Both are possible, but the second one puts more focus on when it happens.

This is the standard verb-second rule in German main clauses.

Abdecken is very natural here because it means to cover up / put a covering over something, especially in practical everyday contexts like food, bowls, tables, etc.

• die Schüssel mit Alufolie abdecken = cover the bowl with aluminum foil

Bedecken also means to cover, but it can sound a bit more formal or descriptive, and it is often used in broader contexts too:

• Schnee bedeckt die Straße. = Snow covers the road.

For kitchen/household actions, abdecken is usually the better everyday choice.

Usually, yes. Die Schüssel most often means bowl.

Depending on context, it can sometimes be translated more generally as dish or container, but bowl is the most direct and common translation here.

So:

• die Schüssel mit Alufolie abdecken = cover the bowl with aluminum foil