Voted Best Answer
May 29, 2022 - 02:08 PM
"der Chef" is in the nominative because it is the subject of the clause "der Chef kommt am Mittwoch".
The main clause is "Ich denke"; the subordinate clause is "der Chef kommt am Mittwoch".
In English we also use the nominative for the subject of the subordinate clause, although we can only see it if we use a pronoun, since we don't use cases for our nouns.
We would say:
I think the boss will come on Wednesday. --> I think he [nominative] will come on Wednesday.
We wouldn't say:
I think him [accusative] will come on Wednesday.
I hope this helps. :-)