not satisfied, caution with the guarantee

I have the device 3 times used to mature wechseln..jetzt I want to change my tires again and realized that the device no longer funktioniert..gekauft 11.2012.erst 1.5 years old and used 3 times ... the answer of the Seller is:

"Because of you described shortcomings and the fact that the goods have already been more than 6 months in use, we have to assume that the deficiencies have been caused by a material or manufacturing defects.

We must reject the warranty claims in this case, as in the context of the burden of proof passes the provision of evidence to the customer.

We ask for your understanding that no further steps are carried out on our part. "