Anna erzählt eine witzige Geschichte.

In a normal German main clause, the finite verb usually comes in position 2. That is one of the most important word-order rules in German.

So in:

Anna erzählt eine witzige Geschichte.

• Anna = position 1
• erzählt = position 2
• eine witzige Geschichte = the rest of the sentence

This is similar to standard English word order in a simple sentence, but in German the verb-second rule is much more strict. Even if you move another element to the front, the verb still stays second:

• Heute erzählt Anna eine witzige Geschichte.
• Eine witzige Geschichte erzählt Anna.

In standard German, first names usually appear without an article.

So you normally say:

• Anna erzählt ...
• Paul kommt ...
• Maria lernt ...

In some regional varieties of German, especially in parts of southern Germany, Austria, and Switzerland, people do sometimes use an article with names in everyday speech, such as die Anna or der Paul. But for standard German learning, Anna without an article is the normal form.

erzählt is the 3rd person singular present tense form of the verb erzählen.

Conjugation in the present tense:

• ich erzähle
• du erzählst
• er/sie/es erzählt
• wir erzählen
• ihr erzählt
• sie/Sie erzählen

Because Anna is she, the sentence uses erzählt.

Because Geschichte is a feminine noun.

The indefinite articles are:

• ein for masculine and neuter in the nominative
• eine for feminine in the nominative

So:

• ein Mann
• ein Kind
• eine Geschichte

In this sentence, Geschichte is feminine singular, so eine is required.

Because in German, adjectives before nouns usually take an ending.

Here, witzig is placed before Geschichte, so it becomes witzige.

Why specifically -e here?

Because the noun phrase is:

• eine = feminine singular article
• witzige = adjective with the correct ending
• Geschichte = feminine singular noun

This is an example of adjective declension. After eine with a feminine singular noun in this pattern, the adjective takes -e:

• eine witzige Geschichte
• eine interessante Idee
• eine kleine Katze

If the adjective came after the verb instead, it would stay uninflected:

• Die Geschichte ist witzig.

It is in the accusative case, because it is the direct object of the verb erzählen.

The sentence answers the question:

What is Anna telling?
→ eine witzige Geschichte

That makes it the direct object.

For feminine singular nouns, the indefinite article is:

• nominative: eine
• accusative: eine

So the article looks the same in both cases. You know it is accusative mainly from its function in the sentence, not from a visible change in the article.

Usually, yes. erzählen often takes something that is being told, and sometimes also a person it is told to.

Examples:

• Anna erzählt eine Geschichte.
  Anna tells a story.

• Anna erzählt dem Kind eine Geschichte.
  Anna tells the child a story.

So eine witzige Geschichte is the thing being told. You can also add an indirect object like dem Kind, mir, uns, and so on.

Yes, it is in the present tense.

German present tense can cover several meanings that English often separates:

• Anna tells a funny story.
• Anna is telling a funny story.
• sometimes even Anna tells funny stories in a habitual sense, depending on context

So without extra context, the German present tense can be a little broader than the English simple present.

Because all German nouns are capitalized.

So:

• Anna
• Geschichte

are capitalized, but words like erzählt and witzige are not, because they are not nouns here.

This is one of the most noticeable spelling rules in German and can help you identify nouns while reading.

A rough pronunciation guide:

• erzählt sounds approximately like air-TSEHLT
• Geschichte sounds approximately like guh-SHIKH-tuh

A few useful details:

• z in German sounds like ts
• ä is somewhat like the vowel in bed, though not exactly the same
• sch sounds like English sh
• ch in Geschichte is the softer German ch sound, not an English k

Also, erzählt is stressed on the second syllable:

• er-zählt

And Geschichte is also stressed on the second syllable:

• ge-schich-te