I spent three and half weeks in Germany during December. Despite it being winter all of the tourist attractions were open, and the Christmas Markets added delicious food and drinks which would be hard to find the rest of the year.
I travelled to Frankfurt, Freiburg, Münich, Füssen, Nuremberg, Dresden, Berlin and Hamburg in that order. Accommodation was generally reasonably priced – 20 for dorm bed, 40 for private room. I mainly stayed at hostels, though stayed in a hotel in Nuremberg. Food was well priced depending what I ate. Restaurants were around 10-15, whereas market food and kebabs were around 3.50-5. I only ate vegetarian when I was here and found plenty of german and international vegetarian food. I used my phone for most navigating and walked a lot, although the trains and trams are very good. The sim card I bought cost €35. The internet last me the whole trip and I was able to send messages with the same sim in Sweden and Turkey, though could not use the internet. Almost everyone speaks English, but they like to be thanked in German and seem to appreciate some language skills from foreigners.