You're welcome.
They are at 18% right now, firmly behind the CDU (Merkel's party), which sits at 33% of the votes. However, even if the AfD were to get the most votes, they likely wouldn't be able to form a majority, as no other party is willing to form a coalition with them. So even if they were to win by getting the most votes, they still most likely wouldn't be able to govern. At least for now. This might change in the next few years and quite a few people are afraid that the CDU might consider a coalition with them in the future, despite claiming repeatedly that they would never consider it.
Edited the numbers, as I have found more recent surveys.