Dieses Gerücht macht mich nervös, weil niemand genau weiß, was stimmt.

This rumor makes me nervous because nobody knows exactly what’s true.

Breakdown of Dieses Gerücht macht mich nervös, weil niemand genau weiß, was stimmt.

• weil: because
• machen: to make
• nervös: nervous
• niemand: nobody
• mich: me
• dieses: this
• wissen: to know
• was: what
• genau: exactly
• das Gerücht: the rumor
• stimmen: to be true

Questions & Answers about Dieses Gerücht macht mich nervös, weil niemand genau weiß, was stimmt.

Why is it Dieses Gerücht and not Diese Gerücht?

Because Gerücht is a neuter noun: das Gerücht.
So in nominative singular you get dieses Gerücht (neuter).
For comparison:

• der Hund → dieser Hund
• die Katze → diese Katze
• das Gerücht → dieses Gerücht

What case is mich here, and why?

mich is accusative. The pattern is jemanden + Adjektiv machen = to make someone (adjective).
So:

• Dieses Gerücht (subject, nominative) macht
• mich (direct object, accusative)
• nervös (predicate adjective describing mich)

Why is it macht mich nervös and not macht mir nervös?

Because machen takes an accusative object in this meaning (to make someone…).
mir (dative) would be used with different constructions, e.g.:

• Das macht mir Angst. (idiomatic: it scares me; literally: it makes fear for me)
  But with nervös, the normal pattern is jemanden nervös machen → mich.

Is nervös an adjective or an adverb here?

It is an adjective used predicatively (a predicate adjective). It describes the object mich as a result of the action: makes me nervous. It does not take adjective endings because it is not attributive (not directly before a noun).

Why is there a comma before weil?

Because weil introduces a subordinate clause, and German normally separates subordinate clauses with a comma:

• Dieses Gerücht macht mich nervös, weil …

Why does the verb go to the end in weil niemand genau weiß, was stimmt?

In a weil-clause (a subordinate clause), the conjugated verb typically goes to the end:

• … weil niemand genau weiß …
  Here weiß is the finite verb, and it comes last in that clause segment.

Why is there another comma before was stimmt?

Because was stimmt is a second subordinate clause (an embedded clause) functioning as the object of weiß.
Structure:

• niemand (subject)
• genau (adverb)
• weiß (verb)
• object clause: was stimmt (what is true)

German marks that embedded clause with a comma: weiß, was stimmt.

Why is it was stimmt and not was ist stimmt or was ist wahr?

• stimmen is a verb meaning to be correct / to be true in many contexts. So was stimmt = what is true / what is correct.
• was ist wahr is also possible and means nearly the same, but stimmen is often more idiomatic in everyday German for what’s correct.

Is was stimmt a question? Why doesn’t it have a question mark?

It is an indirect question (an embedded question), not a direct question. Indirect questions in German use statement punctuation:

• Direct: Was stimmt?
• Indirect: … weiß, was stimmt.

What is the role of genau in niemand genau weiß?

genau here means exactly / precisely / for sure. It intensifies weiß:

• niemand weiß = nobody knows
• niemand genau weiß = nobody knows exactly / nobody knows for sure

Could this use ob instead of was?

Not in this sentence. ob means whether/if and is used when the content is a yes/no issue:

• … weil niemand weiß, ob es stimmt. = because nobody knows whether it’s true.
  was stimmt means what (exactly) is true—it implies multiple details are unclear, not just yes/no.

Does weil always force verb-final word order? I’ve heard weil with verb-second.

In standard written German and in careful speech, weil takes verb-final: weil … weiß.
In some spoken varieties, people use weil with verb-second (V2), e.g. weil niemand weiß es genau, but this is considered informal/non-standard and is usually avoided in writing.

Can I move weil niemand genau weiß, was stimmt to the beginning of the sentence?

Yes. Then the subordinate clause comes first, and the main clause uses inversion (verb in position 2):

• Weil niemand genau weiß, was stimmt, macht mich dieses Gerücht nervös.
  Notice macht comes right after the fronted clause.