New winter tyres with DOT purchased in mid 2015 !!!

Good morning, topic with me: purchase of winter tyres/wheels from private via EBAY classified ads in the range of €2,000.. The wheels were described as follows: “Tyres have only run 1500km, absolutely as new”. I asked the seller for the DOT numbers, because they clearly indicate the age of the tyres. Background is that old tires clearly lose quality and safety (hardening, significantly less wet grip). He wrote to me: “DOT I have to look – the tires I got in June 2020 (this year!) bought for the main investigation -” I relied on it and did not ask for the numbers again explicitly. Now the wheels were sent to us for referral. Profile is actually almost new. However, with the DOT numbers one can see that the two front ones were produced in calendar week 16/2015 and the two rear ones in calendar week 41/2015 and are therefore 5 years or older. There is no legal regulation on how long tyres are In the net you can find this: “The Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V. (BRV) states that tyres up to an age of up to 3 years are considered factory new. Unused tyres with an age of up to 5 years are still considered new. According to ADAC, new tyres should not be older than two years. At Quick Reifenservice only tyres are sold as new products, which according to DOT number are not older than 3 years. Thus you get only new tires. But also tires older than 3 years can be used safely, but then they have a lower service life.” I feel deceived by the seller, he stands on the point that he has provided me with all the information truthfully. This is annoying insofar as we could have had the same wheels with DOT numbers from mid-2017 and end of 2019 for significantly less money. Finally, the indication “absolutely new” and “buried only this What are our chances of “reduction” or even “reduction”? VG and thank you