How do verbs with fixed prepositions work?
Many German verbs require a specific preposition, and this preposition often dictates the case of the following noun/pronoun. You must learn the verb together with its preposition and required case.
Example
warten auf + Akkusativ (to wait for)
denken an + Akkusativ (to think about)
sprechen mit + Dativ (to speak with)
sich freuen über + Akkusativ (to be happy about something present/past)
sich freuen auf + Akkusativ (to look forward to something future)
Example Sentence: Ich warte auf den Bus. (I'm waiting for the bus.)