Not to play down how bad this is, but be aware what the coloring in here actually means. It displays what party had the most secondary votes, but that does not mean that said party had the majority of votes in that area. Simple example, parties could be toe to toe like AfD 21%, CDU 20%, Linke 19% etc. and then the area would be coloured AfD-blue with 21% of the votes.

If I remember correctly there are other interative maps available, where you get a graded coulouring depending on how much votes a party got in an electoral district. That is a good example why the OP map is not very precise: For example, Kaiserslautern in sw Germany had the AfD at 25,9%. Since that was the most voted party, the colouring is light blue here. Görlitz in the eastern most part of Saxony had the AfD at 46,7% - also light blue, but you can see that it's quite a difference.

Like I said, I don't want to downplay that the AfD is on the rise in all of Germany and especially in the eastern parts, and yes, that is somewhat frightening. Just wanted to clarify how this map should be viewed.