However, there’s no need to panic, because in many regions there are varieties of Standard German, which aren't so different and are mutually inteligible. Only some of the phonetics and vocabulary differs, and in some parts of Germany, varieties of German have replaced the local dialects.
Here’s a list of the main ones to keep an ear out for (and possibly a dictionary):
Sorbian (also known as Wendish or Lusatian)
The Sorbs are a slavic minority in Eastern Germany, mainly Saxony. They have their own dialects (Upper and Lower Sorbian), which are co-official to German in that area. Both dialects sound and look distinctively different from German because they have a few extra letters in their alphabet. The Upper Sorbian dialect is spoken in Upper Lusatia, today part of Saxony, by 40,000 people, making it the third biggest minority dialect in Germany. The city of Bautzen is considered the centre of Upper Sorbian culture, and street signs are all bilingual. Despite being a co-official dialect, it is considered to be in danger of extinction. The Lower Sorbian dialect is spoken in Lower Lusatia, today part of Brandenburg, by around 10,000 people. The cultural capital is Cottbus, and although signs are bilingual only one school (or Gymnasium) uses it as the language of tuition.
North Frisian
North Frisian is a minority dialect found in North Frisia, and it has two varieties: one in the mainland and another one in the islands. Although children no longer learn it and it is in danger of becoming obsolete, North Frisian became a co-official language in 2004. It is spoken by approximately 10,000 people, but all its speakers are bilingual in Standard German, so no worries for all those who end up there!
Danish
There is a small community of Danish speakers in Southern Schleswig, on the border with Denmark, where it holds an officially recognised regional language status. Across the border, in Denmark, Standard German is given the same recognition.
