451 from BJ 2012…What to pay attention to…. also convertible

Hello together. I’d like to get a 451. Now I’ve read a lot in recent times and am therefore of the opinion that it should be a SMART from 2012 onwards since many problems have been solved from the period. E.g. here under breakdowns and defects https://www.adac.de/…/detail.aspx?… Now I ask myself what should be paid special attention. Besides, I didn’t find much about the convertible, there are also corners that should be looked at there? Would I be happy about tips.