Dunno if available in Germany, but check out if t-shirts from Northern Playground are available.
They are a blend between merino wool and silk, with a nice and loose fit. Their tees are my favourite, but also offer longsleeves and grampa shirts, socks, beanies, etc. Sustainable, made in the EU, really great products.
I have a Patagonia rainshell which I found dirt cheap on sale many yeara ago and it is absolutely fantastic. Packs small into its own little puch and the water repellant hasn't failed me yet