Op lives in Germany and ( possibly) with an Eastern European background so a lot of the advice on here won’t be relevant as it will relate to British UMC style
Okay, OP... I can possibly help here. I grew up in Germany, most of my family still live there and we were very much part of the 'obere Mittelschicht'. My parents still live where I grew up, which is known as the wealthiest area of a city known to be 'snobby'. One of my closest friends lives in Munich (which is probably the 'centre of wealth and glamour' in Germany).
The funny thing is that upper middle class Germans are a little anglophile. They WILL wear Barbour & co. constantly – however, UNLIKE their British counterparts, their Barbour jackets will look immaculate as though it's the first time they have ever been worn. Boots and shoes are always polished.
Get yourself loads of quality (expensive) blazers. Pair them with trousers, jeans, anything. Get some pearl earrings. Get shoes from TODS, etc. Have a nice bag.
It's the same as everywhere really... but much more polished. Like you can't get away with the British UMC style over there.
If you ARE in Bavaria, there are also other sets of rules... like if you ever wear a Dirndl, get a proper one that costs around EUR300-500 and not those cheap ones that look like Halloween costumes.
Similarly, your hair must be immaculate. Not overkill GHD straightened, but 'effortlessly' chic... the old lady who used to live across the street from us used to achieve this by getting her hair blowdried professionally every week.
And this is why I am somewhat relieved I didn't marry the rich German guy my parents hoped I'd marry who was one of my closest friends as a teenager. His mom spent like forever getting ready every day. 