Galaxy A3 touch back stopped after downgrading from lollipop to kitkat

Hello . I upgraded my A3 (SM-A300H) to lollipop. After a while I wanted to return to kitkat because lollipop freezes too much . I have downloaded the kitkat official rom for a300h and then wiped cache and data. Everything is OK but the touch back button and the task view button not worked. after that I reflashed the lollipop rom and worked again . How can I downgrade to kitkat without any errors and the touch buttons working?