Meine Nichte spitzt den Buntstift mit dem Spitzer, bevor sie weiterzeichnet.

Because Nichte is a feminine noun, and here it is the subject of the sentence, so it is in the nominative case.

The possessive adjective mein- changes its ending depending on gender, number, and case:

• mein Neffe = my nephew
• meine Nichte = my niece

So meine Nichte is the correct nominative feminine form.

Den Buntstift is the direct object of spitzt — it is the thing being sharpened.

The noun Buntstift is masculine: der Buntstift.
Masculine nouns change in the accusative:

• nominative: der Buntstift
• accusative: den Buntstift

So:

• Meine Nichte = the subject
• spitzt den Buntstift = sharpens the colored pencil

Because the preposition mit always takes the dative case.

Spitzer is a masculine noun: der Spitzer.
In the dative singular, der becomes dem:

• nominative: der Spitzer
• dative: dem Spitzer

So mit dem Spitzer means with the pencil sharpener.

Here, spitzen means to sharpen.

So den Buntstift spitzen means to sharpen the colored pencil.

In everyday German, you may also hear anspitzen for sharpening a pencil:

• einen Bleistift anspitzen

But spitzen is also perfectly understandable in this context.

Buntstift is a compound noun:

• bunt = colorful / colored
• Stift = pencil, pen, stick-like writing tool

A Buntstift is usually a colored pencil.

German often builds nouns by combining smaller words into one larger word.

Because bevor introduces a subordinate clause, and in German subordinate clauses are normally separated by a comma.

So:

• Meine Nichte spitzt den Buntstift mit dem Spitzer, bevor sie weiterzeichnet.

That comma is required in standard written German.

Because bevor is a subordinating conjunction. Subordinating conjunctions send the finite verb to the end of the clause.

Compare:

• main clause: Sie zeichnet weiter.
• subordinate clause: bevor sie weiterzeichnet

That is a very common German pattern:

• weil sie müde ist
• dass er kommt
• wenn wir Zeit haben
• bevor sie weiterzeichnet

Because weiter can combine with zeichnen to form weiterzeichnen, meaning to continue drawing.

In this sentence, the finite verb is at the end because of bevor, so the whole verb form appears together as weiterzeichnet.

Compare:

• main clause: Sie zeichnet weiter.
• subordinate clause: ..., bevor sie weiterzeichnet.

This is similar to how separable-style combinations often behave in German: split in a main clause, joined at the end of a subordinate clause.

In many contexts, yes, you may see both weiterzeichnen and weiter zeichnen. German spelling and usage can allow some variation here.

For a learner, the most useful thing to remember is:

• Sie zeichnet weiter. = She continues drawing.
• ..., bevor sie weiterzeichnet. = ...before she continues drawing.

So even if you encounter variation, the grammar pattern is the same.

Here, sie refers back to meine Nichte.

German often uses a pronoun in the subordinate clause instead of repeating the noun:

• Meine Nichte ... bevor sie weiterzeichnet.

That sounds natural, just like English would usually say before she continues drawing instead of repeating my niece.

Yes. You can also say:

• Bevor sie weiterzeichnet, spitzt meine Nichte den Buntstift mit dem Spitzer.

That is also correct.

When a subordinate clause comes first, the main clause still follows the verb-second rule, so the conjugated verb spitzt comes immediately after the first clause.

No. It is a natural way to say with the pencil sharpener, but German could also express the idea in other ways depending on style and context.

For example, German often uses mit to show the tool used to do something:

• mit dem Messer schneiden = cut with a knife
• mit dem Stift schreiben = write with a pen
• mit dem Spitzer spitzen = sharpen with a sharpener

So this sentence uses a very common structure: action + object + mit + instrument.

Because German main clauses usually follow the verb-second rule.

The first element here is the subject:

• Meine Nichte | spitzt | den Buntstift | mit dem Spitzer

So the conjugated verb spitzt comes second.

This is one of the most important word-order rules in German main clauses.