Brush, compatible with Philips HX2014,

I ordered the brush because the Philips still works very well as a unit and in front of all the battery.
The material of the brush head is different as expected (Nachahmeprodukt) from the originals
Spare parts, which I have used for years. In the first week of use, the bristles appear to be very soft completely.
Later, the outer bristles diverge and are brush-like soft. Maybe that's healthy (gum massage?), But I do not like. After a month of use, the inner bristles are bent or deformed or compressed and very hard with decreasing brush cleaning function (chemical reaction with the Zahnchreme?).
I will no longer buy these spare brushes, but a complete new toothbrush if I
Brush heads have worn.