Magdalena:
Maggie,
Magda, or
Lena.
Magda sounds older to me, so if it is a kid or a teenager I'd prefer
Maggie or
Lena.
Sofia: Just
Sofia.
Sofie is alright, but I don't think it's needed.
Larisa: No nn needed.
Josephine:
JoAnika: No nn needed;
Ana, Ani, or
Annie if anything.
Anastasia:
Ana. Maybe Stasia or
Asia. Although I know a few Anastasias who go by
Anastasia all the time, and it isn't as overly long as you'd expect.
Gabriel:
Gabe, but not really needed.
Emanuel:
Manuel, if anything.
Sebastian: Seb. I like
Bastian too, but for some reason I prefer
Bastian as a full name and Seb as a short form of
Sebastian.
Dominik:
Dom or
Nik, but not necessarily needed.
Simon: None needed.
Branimir:
Bran, which is probably my favorite male nn of all time. :)