A nostalgic young writer from Germany is getting his dream scholarship for a US college, but is facing the death of his grandfather and the first meeting with his father after 15 years, and can not decide whether he can leave behind his home and family and friends in order to beginning a new life. But time is running out and the acceptance period expires.

FFF is right. Unless you state in your logline why the young writer is nostalgic, the word just hangs there. That he misses his grandfather doesn't have to be elaborated on in the logline. Lose nostalgic, I say.

You won't like my answer.

A movie about growing up -- leaving our homes to go out into the world and do something meaningful with our lives.

We know act 2 is about making a decision: should I use my talent and move forward toward my dreams or sit at home and pine about my past. ?

If I was the grandfather it would be: dude are you kidding? ?Move on, I'm going to die anyways.?

Same thing for the father: all normal parents encourage ?the birds in their nest to seize the day, go out there and fly.

Maybe sentimental or immature is better description of the MC:

After an immature film maker receives a scholarship to attend his goal-in-life film school, he struggles to leave home.

Or if the family is somewhat dysfunctional:

After receiving a scholarship to a prestigious film school, a talented filmmaker struggles to break free from his conniving family.

Sorry, just my opinion.

The character is nostalgic because of the confrontation with his past. He has a class reunion after years and sees all his old classmates and he wants the time back when he was walking with his grandfather.
He can't let behind the past. Something like that.

"After a nostalgic german student is getting his dream scholarship for a prestigious US film school, he is confronted with the death of his grandfather and the meeting with his father and has to make a decision on his future before the acceptance period expires."