Well, I just made a new account just to see what happens, clicked Politics -> German something something as my preferences, and Twitter is suggesting to me:
Manuela Schwesig
Ministerpräsidentin von Mecklenburg-Vorpommern
Stellvertretende SPD-Parteivorsitzende
A ton of official government agencies, then a list of Turkish people (I guess it knows exactly the part of the city where I live 8)), Bushido and some other Musicians... FC Bayern München.. Veltins...
I just clicked 'Follow and Continue'.
Now, I don't know what the Turkish people in my timeline say, but aside from a few SPD-related posts, I don't see much about politics.
If I go into the Politik Hashtag, I see a lot of posts from left-wing people, ironically including this one:
"Die angekündigte Enteignung von Flüchtlingen in Österreich ist ein neuer Tiefpunkt der Menschlichkeit gegenüber Schutzsuchenden. Eine Schande für die Christdemokratische Parteienfamilie in Europa!"
In the middle I see a post from an official AfD Account, but it's not very controversial and has like... 10 times more likes than every other post there, so I'd expect it to be there.
As I scroll further through the top posts of the hashtag I do see some pro-AfD, anti-Immigration posts, but they're outnumbered - and heavily so - by posts that are clearly not in agreement with them.
So my new account - from somebody who is almost literally "new to twitter" as I only have a fake account so I can read the "posts and replies"-tab - doesn't really share the experience you made. I think it's either just bad luck, or selective perception.