Meine Schwester schließt den letzten Tab, bevor sie die Hausarbeit speichert.

Because bevor introduces a subordinate clause. In German subordinate clauses, the conjugated verb usually goes to the end.

So:

• Main clause: Meine Schwester schließt den letzten Tab
• Subordinate clause: bevor sie die Hausarbeit speichert

This is one of the most important German word-order patterns to learn.

No. German normally needs an expressed subject in each clause.

So even though sie refers back to meine Schwester, you still say:

Meine Schwester schließt den letzten Tab, bevor sie die Hausarbeit speichert.

Leaving out sie would be ungrammatical here.

Because den letzten Tab is the direct object of schließt. The verb schließen takes the accusative case.

• der Tab = nominative masculine singular
• den Tab = accusative masculine singular

Since Tab is masculine, the article changes to den in the accusative.

The adjective also changes:

• nominative: der letzte Tab
• accusative: den letzten Tab

That is the adjective ending. In den letzten Tab, the adjective letzt- follows a definite article (den), so it takes the weak ending -en in masculine accusative singular.

So the pattern is:

• der letzte Tab
• den letzten Tab

This is a very common adjective-ending pattern in German.

It is an object, but Hausarbeit is feminine, and in the singular the feminine definite article is die in both nominative and accusative.

So:

• nominative: die Hausarbeit
• accusative: die Hausarbeit

That is why the article looks the same here.

In this context, Hausarbeit usually means something like term paper, essay, or written assignment rather than literal housework.

German words can be a little context-dependent here. In academic or school contexts, Hausarbeit often means a paper you write and then save on a computer, which fits this sentence well.

Yes, they are different.

• bevor = before, as a conjunction introducing a clause
• vor = before/in front of, usually as a preposition

Here you need bevor because it connects two actions:

My sister closes the last tab before she saves the paper.

You could not use vor in place of bevor in this sentence.

Yes. Both verbs are in the present tense:

• schließt
• speichert

German present tense can cover both:

• a habitual action
• a current action
• sometimes even a near-future action, depending on context

So this sentence could mean either:

• this is what she usually does, or
• this is what she is doing now

German does not require a separate progressive form like is closing or is saving.

The dictionary forms are:

• schließen = to close
• speichern = to save / store

In the sentence, both are in third-person singular present tense, because the subject is meine Schwester.

So:

• meine Schwester schließt
• sie speichert

Because all German nouns are capitalized.

That is a standard rule in German spelling. So in this sentence:

• Schwester is a noun
• Tab is a noun
• Hausarbeit is a noun

Their capitalization helps you identify them as nouns.

Yes. Tab is a common borrowed word in German, especially in computer and browser contexts.

You will often hear and read:

• der Tab
• die Tabs

There are more formal German alternatives in some contexts, but Tab is very common in everyday tech language.

Yes. You can also say:

Bevor sie die Hausarbeit speichert, schließt meine Schwester den letzten Tab.

That is completely correct. When the subordinate clause comes first, the main clause still follows the verb-second rule, so the conjugated verb schließt comes right after the opening clause.