Manche Kollegen sind ein wenig neidisch auf ihren Erfolg.

Manche means roughly “some” in a general, somewhat vague way. It suggests “not all, but a noticeable number”.

Comparisons:

• manche Kollegen – some colleagues (fairly neutral, can feel a bit more general or slightly literary/formal than einige)
• einige Kollegen – some / several colleagues (often implies a limited but not tiny number)
• ein paar Kollegen – literally a few colleagues; sounds more casual and often suggests a smallish number

All three are possible here, but:

• manche and einige are closer in tone.
• ein paar can sound more like “a couple of / a few”, often slightly more informal.

Kollege (colleague) is a so‑called weak noun in the singular (der Kollege, den Kollegen, etc.), but in the plural it’s regular:

• Singular:

  • Nominative: der Kollege
  • Accusative: den Kollegen
  • Dative: dem Kollegen
  • Genitive: des Kollegen

• Plural:

  • Nominative: die Kollegen
  • Accusative: die Kollegen
  • Dative: den Kollegen
  • Genitive: der Kollegen

In this sentence, Kollegen is nominative plural (subject of the sentence), so Manche Kollegen = “some colleagues”.

Breakdown:

• Manche Kollegen – nominative plural
  They are the subject: the ones who are jealous.

• sind – verb (3rd person plural of sein).

• ein wenig neidisch – predicate adjective phrase describing the subject (no case ending here because it’s predicative).

• auf – preposition used with accusative in this expression.

• ihren Erfolg – accusative singular, direct object of the preposition auf.

So structure-wise:

• Subject (Nom.): Manche Kollegen
• Verb: sind
• Predicate adjective: ein wenig neidisch
• Prepositional object (Acc.): auf ihren Erfolg

German only adds adjective endings in attributive position – when the adjective directly modifies a noun:

• ein neidischer Kollege – a jealous colleague
• die neidischen Kollegen – the jealous colleagues

In this sentence, neidisch is predicative, coming after “sein” and describing the subject, not directly modifying a noun:

• Kollegen sind neidisch.
• Manche Kollegen sind ein wenig neidisch.

Predicative adjectives in German do not get endings, just like in English: “The colleagues are jealous” (no extra ending).

In German, the adjective neidisch normally combines with the preposition auf (+ accusative):

• neidisch auf jemanden / etwas sein – to be jealous / envious of someone / something

Examples:

• Sie ist neidisch auf ihre Schwester. – She is jealous of her sister.
• Er ist neidisch auf deinen Erfolg. – He is jealous of your success.

von or über do not work with neidisch in standard German.
Think of neidisch auf as a fixed combination you should memorize.

The preposition auf can take either accusative or dative, depending on meaning:

• Accusative (direction / “onto”) or with some fixed expressions.
• Dative (location / “on, on top of”).

With neidisch, auf is always used with the accusative:

• neidisch auf + Akkusativ
  → auf ihren Erfolg

auf ihrem Erfolg (dative) would sound wrong in this context because the idiom requires the accusative.

The form of ihr- has to match:

1. the gender and number of the noun
2. the case governed by the preposition

Here:

• Erfolg is masculine: der Erfolg.
• After auf (with neidisch), we need accusative.
• Masculine accusative with ihr- → ihren.

Quick table for masculine singular of ihr- (“her/their” depending on context):

• Nominative: ihr Erfolg
• Accusative: ihren Erfolg
• Dative: ihrem Erfolg
• Genitive: ihres Erfolgs

So ihren Erfolg is exactly what we need: masculine accusative.

By itself, ihren can mean either:

• “her” (possessive referring to sie singular)
• “their” (possessive referring to sie plural)

German relies on context to decide which is meant.
In a real text, you’d normally know from earlier sentences whether we’re talking about one woman’s success or several people’s success.

This sentence out of context is ambiguous in exactly the same way as English “her success” vs “their success” is ambiguous if you only see “their”.

All three can often mean “a little / somewhat / a bit”, but they differ slightly in tone:

• ein wenig

  • Slightly more neutral / careful / sometimes a bit formal.
  • Often used in writing or polite speech.
  • Fits well: ein wenig neidisch = “a little bit jealous”.

• ein bisschen

  • Very common and informal, everyday spoken German.
  • Manche Kollegen sind ein bisschen neidisch auf ihren Erfolg. sounds very natural in conversation.

• etwas

  • Means “somewhat, rather, a bit” (or “something” in other contexts).
  • Manche Kollegen sind etwas neidisch auf ihren Erfolg. = “Some colleagues are somewhat / rather jealous of her/their success.”

All three are grammatically fine here; choice is about style and nuance.

Yes, that alternative is grammatically correct:

• Manche Kollegen sind ein wenig neidisch auf ihren Erfolg.
• Manche Kollegen sind auf ihren Erfolg ein wenig neidisch.

Both are fine. The difference is mostly rhythm and focus:

• Original: more neutral, flows very naturally.
• Variant: puts a bit more weight on auf ihren Erfolg (on what they are jealous of) by placing it earlier in the predicate.

German allows fairly flexible placement of adverbs and prepositional phrases, as long as the core order (subject – finite verb – rest) is respected in main clauses.

Yes, that’s also grammatically correct:

• Manche Kollegen sind … – Some colleagues are … (plural)
• Mancher Kollege ist … – roughly some a colleague is … → better English: Some colleagues are … or More than one colleague is …

Differences:

• Manche Kollegen (plural) is the most natural, neutral phrasing.
• Mancher Kollege (singular) sounds a bit more literary or old‑fashioned and is used less in everyday speech.

Meaning-wise, both point to not all colleagues, but some. The plural version is more common.

Both can be translated as “jealous”, but they’re used differently:

• neidisch (auf) – envy of things or achievements someone else has:

  • neidisch auf ihren Erfolg – jealous of her/their success
  • neidisch auf sein neues Auto – jealous of his new car

• eifersüchtig (auf) – usually jealousy in personal relationships:

  • eifersüchtig auf den neuen Freund – jealous of the new boyfriend
  • eifersüchtig auf andere Kolleginnen – jealous of other female colleagues (in an emotional/relational sense)

For success (Erfolg), neidisch is the natural choice.
eifersüchtig auf ihren Erfolg would sound odd in standard usage.

• Manche is capitalized because it’s the first word of the sentence.
• Kollegen is capitalized because it’s a noun, and all nouns are capitalized in German.

If manche appeared in the middle of a sentence, it would normally be lower-case:

• Ich kenne manche Kollegen nicht gut. – I don’t know some colleagues well.