How to choose a firmware before downgrading Andriod version?
According to this site, this is for Region XEO, which would be Poland, located here.  You can't just choose any version and have it work, and Samsung is known to not allow you going backwards in firmware versions due to a lock in the bootloader preventing this.  You may be able to go back to 5.1.1, but most likely not 2 Android versions backwards, and even going back to 5.1.1 may not be possible.