If it is a consumer business (a contract between entrepreneur and consumer), warranty claims can neither be excluded in the general terms and conditions nor in side agreements nor in single contracts. Only for used goods it can be expressly agreed that the 2-year-period is reduced to 1 year. A vehicle for example is regarded as used, if it was licensed for altogether 12 months for public traffic.
In no case can the regulations of guarantee replace or rescind the legal seller´s warranty.