The correct option is
C many times
In the given sentence, 'been to Germany' indicates that the sentence is talking about visiting Germany. Thus, it can be said that the question is asking the number of times the subject has been to Germany. The answer must, therefore, indicate the above meaning.
Option A is incorrect. 'much time' indicates that the question is asking for what period of time the subject has been in Germany. Also, the preposition 'to' does not agree with it. Thus, it is incorrect.
Option B is incorrect. 'long for' indicates that the question is asking for what period of time the subject has been in Germany. Also, the preposition 'to' does not agree with it. Thus, it is incorrect.
Option C is correct. 'many times' indicates that the question is asking about the number of time the subject has been to Germany. Thus, it conveys the correct meaning and is the correct answer.
Option D is incorrect. 'long ago for' indicates that the question is asking what period of time ago and for what period of time the subject has been in Germany. Also, the preposition 'to' does not agree with it. Thus, it is incorrect.