Anomaly Abgasreinigung

My car 2004 Model Diesel Peugeot 307 2.0 HDI 136Beygir. There is a strange and very frustrating malfunction in my car recently. I bought a new one and assembled it myself. 2 weeks I used the tool without any problems. After 2 weeks this problem started again. I checked the Air Filter and when I saw that it was very dirty, I replaced it with a new one. I heard a beep, and then it gave the error "Anomalie Abgasreinigung" on the screen.After that, a warning lamp came on the screen where the tachometer was located.Then I went back to the mechanic, after the airflow meter change, he connected to the device again and said that the error code had to be reset, and after resetting the vehicle in this type of problem 3. 15-20 Km up to 80 to 100 vehicles in gear at high speed accumulated in the filter He said that he would burn the dirt, the institution. He said that this problem might have occurred because I did not use the vehicle for a long time. They said that there was another tank and an oil or gas called ADITIV might have run out.