Student or Learner
The manager found his responses to many of his questions at the interview to be evasive.
Is this sentence OK?
However, all the little prepositions and infinitives make it somewhat difficult to follow, and the use of "his" to refer to two different people is confusing. It would be more clear if you placed the adjective closer to the noun it modifies ("responses"); also, "to be" isn't required.
Here's my suggestion:
At the interview, the manager found his responses to many of
histhe questions (to be) evasive.
At the interview, the manager found many of his responses
to his questions to beevasive. [The words "interview" and "responses" imply that there were questions... But this is a matter of style, not grammar!]