Any know Berlin really well? Some questions.

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Not quite a holiday question but not sure where to put this.
Hoping there’s some people on here who live/have lived in Berlin fairly recently. My DS is planning on going on a full year Erasmus (not from UK) study exchange to Berlin. The uni is moving this year to the Neukölln area, near the Sonnenallee S-bahn station. They don’t have student halls so he will have to look for accommodation. They provide links etc to private providers and accommodation websites.
I’m wondering if people could suggest good areas that would be safe, commutable or walkable. Not sure whether he should be looking at Neukölln itself or not. I haven’t been to Berlin since the 90s and then only got a couple of days. Just hoping for local, recent advice. From googling it seems the opinions of this area vary ‘up and coming, trendy’ to ‘avoid, dangerous’. Danke!

Hi there, I've spent a lot of time in Berlin over the years.
As a younger person I think he would enjoy Neukoln, it's very cool and vibrant. If safety is the most important the best areas for them would be Freidrichschain near boxhagenerplatz. I would avoid Kreuzberg as whilst it's a very cool place there are some dodgy parts. Prenzlauerberg is very beautiful and safe, central too. Bit more family orientated. I would live here if I moved to Berlin. Hope that helps!