Other tires on it than in the vehicle license?

Moin, I drive a Golf 7 from 2012 which still has its first tires on it and now has almost 25tkm on the clock. It’s GJR. With now almost 7 years I would like to change them. On top are currently 205/55 R16 91V (Goodyear Vector 4Seasons), but in the vehicle license is 205/50 R17 93V. I have the car now almost 1 year. The dealer told me that this is still the first tire. The tires are from KW 40 in 2012. That would get there. Can that be? Why is there something in the bill? other? Why would someone buy 16 inch rims when 17 is in appearance? Plan to drive the car from Hamburg to Frankfurt next week, so I’m also unsure if it’s good to put on new tires beforehand or rather drive the old ones. What could happen?