Apple watch connection issues

Hi! Today was a bad day for me. I bought a new Apple Watch "series 3 brand new" from a shop. I got scammed and it was a series 2 (payed €380). I tried connecting it to my iPhone 7 (IOS 13) and iPhone Xr (IOS 13) but both failed. My iPhone 7 was running 12.4 and I tried connecting the watch. Then I canceled the pairing to and updated to ios 13 on my iPhone 7. When I then tried connecting the app just froze. Same on Xr. I got another iPhone 7 running IOS 12.1.4 Beta which then told me I had to do a software update. When I agreed the app told "watchOS 3 is up to date". Then I grabbed another iPhone 7 running IOS 11.4 Beta which did the same thing. When I try to connect manually the code generates (although the screen is showed with the apple watch (code))

Is it because the firmware is to old to connect to iOS 13?