Come to Berlin in May, June or August.
I excluded July. According to my subjective impression July’s weather is worse.
Berlin is fun. In summer!
I wouldn’t recommend winter time.
Not much to do and to see.
You can see people in metro with a grumpy face. And it is dark most of the day.
February is the coldest month (subjectively).
March, April, September, October are rainy.
Go in summer!
It’s Europe. All good.
Just be careful about your liver, when doing heavy drinking and partying ;-)
There are pickpockets for sure. Watch your belongings.
Don’t get nervous about places like Hermannplatz, Kottbusser Tor or Görlitzer Bahnhof. They are not that dangerous.
Also Marzahn is not too bad.
Enjoy the city!
You can get everywhere by "BVG", public transport. Metro, bus and trains are connected to one big network. Buy a weekly ticket.
Metro and trains un until 1pm Sunday to Thursday. Later you can use night busses. On the weekend everything running all night.
Berlin is cheap compared to other big cities like Paris, London or in the US.
I can only guess since I live in Berlin.
There are many possibilities for accommodation:
hostels, hotels, Air BnB, Couchsurfing etc.
history and nightlife
["U" ~ metro]
Akazienstraße (Schöneberg): bars and restaurants - small area, just this street.
U Eberswalder Str (Prenzlauer Berg): area with bars and nightlife
GM26, Gutsmuthsstraße (Steglitz): cool bar
(Simon- Dach- Straße (Friedrichshain): bars but touristy)
U Schlesisches Tor (Kreuzberg): the whole area is full of bars and clubs
U Oranienburger Straße / Hackescher Markt (Mitte): check out Monbijoupark and all around