Answer:
The conflict strategy would be to Relinquish your interest for that of your friend considering the fact that it is his birthday.
Step-by-step explanation:
If we take a good look at the narrative in the question, it states that the friend has an upcoming birthday which is supposedly a special day to him.
We also can see from the narrative of the question that there exist a conflict of interest between the two parties involved.
So, to properly resolve this type of conflict of interest without actually creating or damaging the reputation of the friendship, we adopt the strategy which involves Relinquishing an ongoing interest in watching the movies Harry Potter.
It is also good to know that the word Relinquish simply means to let go of an ongoing interest in something which is consequentially likely to damage the reputation of anther relatively greater thing.