Die Erdbeeren sind heute etwas sauer, aber mit Sahne schmecken sie gut.

Because Erdbeeren is plural here: strawberries.

• Singular: die Erdbeere = the strawberry
• Plural: die Erdbeeren = the strawberries

In German, the definite article for all plural nouns in the nominative is die, regardless of gender.

So:

• die Erdbeere = singular
• die Erdbeeren = plural

Because the subject die Erdbeeren is plural.

The verb sein changes depending on the subject:

• ich bin
• du bist
• er/sie/es ist
• wir sind
• ihr seid
• sie/Sie sind

Since die Erdbeeren = they / the strawberries, German uses sind.

Because sauer is not being used before a noun here. It is used after the verb sein as a predicate adjective.

Compare:

• saure Erdbeeren = sour strawberries
  Here, the adjective comes before the noun, so it takes an ending.
• Die Erdbeeren sind sauer = The strawberries are sour
  Here, the adjective comes after sind, so it does not take an ending.

The same thing happens with gut later in the sentence:

• gute Erdbeeren
• Die Erdbeeren schmecken gut

Here etwas means somewhat, a little, or rather.

So etwas sauer means a little sour or somewhat sour.

Both etwas and ein bisschen can work in many contexts:

• etwas sauer
• ein bisschen sauer

But etwas is often a bit more compact and slightly more neutral in style. In this sentence, it sounds very natural.

German word order is flexible, but the conjugated verb usually stays in second position in a main clause.

So in:

Die Erdbeeren sind heute etwas sauer

• Position 1: Die Erdbeeren
• Position 2: sind
• then: heute etwas sauer

heute is a time expression, and it fits naturally after the verb here.

You could also move things around for emphasis, for example:

• Heute sind die Erdbeeren etwas sauer.

That would put more focus on today.

Because German is expressing a slightly different idea.

• sind sauer = they are sour
• schmecken gut = they taste good

So the sentence contrasts two ideas:

• The strawberries are somewhat sour today,
• but with cream, they taste good.

This is very natural in German. Schmecken is commonly used for how food tastes.

Because after aber, this is still a main clause, and in a German main clause the conjugated verb normally comes in second position.

The second clause is:

aber mit Sahne schmecken sie gut

Here:

• Position 1: mit Sahne
• Position 2: schmecken
• then: sie
• then: gut

So the word order is correct because mit Sahne has been placed first for emphasis.

You could also say:

• Aber sie schmecken mit Sahne gut.

That is possible, but it sounds less natural here. The version with mit Sahne first emphasizes the important condition: with cream.

Here sie refers to die Erdbeeren.

Since Erdbeeren is plural, sie means they.

German uses:

• sie = she or they, depending on context
• Sie = formal you

Here it is lowercase sie, so it is not formal you. The context makes it clear that it means they, referring back to the strawberries.

Because German often uses a noun without an article when talking about a substance or ingredient in a general sense.

So:

• mit Sahne = with cream

This means cream as an accompaniment, not a specific previously mentioned cream.

If you said mit der Sahne, that would usually mean with the cream, referring to a specific cream already known from the context.

For the same reason as sauer: gut is a predicate adjective/adverb-like form after the verb, so it does not take an ending here.

Compare:

• gute Erdbeeren = adjective before a noun, so it takes an ending
• Die Erdbeeren schmecken gut = after the verb, no ending

This is a very common pattern in German:

• Das Wetter ist schön.
• Der Kaffee schmeckt gut.
• Die Kinder sind müde.

No. Aber does not send the verb to the end.

It is a coordinating conjunction, like but in English. After aber, you usually get normal main-clause word order.

So:

• Die Erdbeeren sind heute etwas sauer, aber mit Sahne schmecken sie gut.

That is different from a subordinating conjunction like weil:

• ..., weil sie mit Sahne gut schmecken.

With weil, the conjugated verb schmecken goes to the end.

Yes, that is possible, but it is slightly different in nuance.

• Die Erdbeeren sind heute etwas sauer describes a property: they are somewhat sour.
• Die Erdbeeren schmecken heute etwas sauer focuses more directly on how they taste.

In everyday language, both can work. The version with sind sauer is very natural when describing fruit that is not very sweet or is a bit tart.

Usually yes, but it can cover a slightly broad range depending on context.

With food, sauer can mean:

• sour
• tart
• acidic

So for strawberries, etwas sauer might sometimes sound closer to a bit tart in natural English, even though sour is the direct meaning.

That is why the sentence can still make sense together with but with cream they taste good: the strawberries are a bit tart, but the cream balances the flavor.