Ich kaufe heute Himbeeren, weil sie im Angebot sind.

Because weil is a subordinating conjunction meaning because. In German, a clause introduced by a subordinating conjunction usually sends the conjugated verb to the end.

So:

• Ich kaufe heute Himbeeren = main clause
• weil sie im Angebot sind = subordinate clause

Compare:

• Sie sind im Angebot. = They are on sale.
• ..., weil sie im Angebot sind. = ..., because they are on sale.

That final sind is one of the most important word-order patterns in German.

Here, sie means they.

It refers to Himbeeren (raspberries), which is plural. Since Himbeeren is plural, the matching pronoun is sie = they.

German sie/Sie can mean different things:

• sie = she
• sie = they
• Sie = you (formal)

In this sentence, it must mean they, because it refers back to Himbeeren.

German often leaves out the article with plural nouns when talking about an indefinite amount of something, especially food or shopping items.

So Ich kaufe heute Himbeeren is very natural and means something like:

• I’m buying raspberries today
• I’m buying some raspberries today

You could also say:

• Ich kaufe heute die Himbeeren = I’m buying the raspberries
• Ich kaufe heute einige Himbeeren = I’m buying some raspberries
• Ich kaufe heute Himbeeren ein = I’m shopping for raspberries today

Without an article, it sounds general and natural here.

Himbeeren is in the accusative case because it is the direct object of kaufe.

Ask: What am I buying?
Answer: Himbeeren

So:

• Ich = subject, nominative
• Himbeeren = direct object, accusative

In the plural, many German nouns look the same in nominative and accusative, so the form Himbeeren does not change here.

im Angebot means on sale, on special, or being offered at a reduced price.

It is a fixed expression:

• im = contraction of in dem
• Angebot = offer

But you usually should not translate it word-for-word as in the offer. The natural meaning is:

• Die Erdbeeren sind im Angebot. = The strawberries are on sale.
• Butter ist diese Woche im Angebot. = Butter is on special this week.

So in your sentence, weil sie im Angebot sind means because they are on sale.

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

In your sentence:

• Ich = position 1
• kaufe = position 2
• heute = later in the sentence

So this is correct:

• Ich kaufe heute Himbeeren.

You can also move heute to the front for emphasis:

• Heute kaufe ich Himbeeren, weil sie im Angebot sind.

That is also correct, but then kaufe must still stay in second position.

What you cannot do in a normal statement is:

• Heute ich kaufe ... ❌

Yes, but the word order changes.

With weil, the verb goes to the end:

• Ich kaufe heute Himbeeren, weil sie im Angebot sind.

With denn, the clause keeps normal main-clause word order:

• Ich kaufe heute Himbeeren, denn sie sind im Angebot.

Both mean because, but they are used a little differently:

• weil is more common in everyday speech
• denn can sound a bit more formal or written

So both are possible, but you must not keep the same word order.

Because all German nouns are capitalized.

So:

• ich = not capitalized
• heute = not capitalized
• Himbeeren = capitalized, because it is a noun
• Angebot = capitalized, because it is also a noun

This is a basic rule in German spelling.

Exactly.

German distinguishes between:

• sie = she or they
• Sie = formal you

In your sentence, sie is lowercase because it refers to Himbeeren and means they.

So:

• weil sie im Angebot sind = because they are on sale
• weil Sie im Angebot sind would mean something like because you are on sale, which makes no sense here

Capitalization matters a lot with sie/Sie.

Yes, that is possible, but it sounds a little different.

• Ich kaufe heute Himbeeren is the most neutral version.
• Ich kaufe Himbeeren heute puts a little more focus on Himbeeren before heute, depending on context.

German word order often changes emphasis rather than basic meaning. For learners, the safest and most natural version is:

• Ich kaufe heute Himbeeren, weil sie im Angebot sind.

That is a very standard sentence structure.