Your worries are justified - in 1928, the Nazi party NSDAP only scored 2.6%. 5 years later, it would take over the country and create the most genocidal dictatorship in history. However, the future is not set in stone by a snapshot of public polling. The next federal election is only in 2.5 years.
Here is public polling from 2017 to 2020. CDU in a clear lead with >40%, AfD stable above 10%, a lot of the times even hitting >15%.
Now compare it to the election result in 2021:
A lot can and will happen before the next election.,