Some of the popular xootrs are rated for 800lb / 362kg.

It's a pricey USA brand ($300ish). You can get them shipped to germany through amazon USA but the customs will cost you $150 to ship it to germany (maybe something to pick up on holiday?):

Example https://www.amazon.com/dp/B07N7GP4DS

For something available in germany have you checked out the Hudora big wheel 230? It's rated at 120kg and sells for as low as 99 euros on amazon de (if you can stomach pink/rosa):

https://www.amazon.de/-/en/Hudora-BigWheel-Folding-Scooter-Single/dp/B00LPJUY38/

I'm guessing the 100kg limit you see on so many of the big name scooters is because the safety standard for scooters, EN 14619:2019, is specific to scooters designed for folks under 100kg. I'm guessing the good ones can do a bit over 100kg:

https://www.tuvsud.com/en/e-ssentials-newsletter/consumer-products-and-retail-essentials/e-ssentials-12-2019/eu-kick-scooters-standard-en-14619-2019-published

Edit: Just wanted to add be careful out there! I remember years ago I saw my first full size adult on an adult size scooter. An old man scooting with his grandson. Oh how cute I thought then in the next instant somehow he fell on his but even though they were just sitting at a stop light or cross walk. I've been scooting now for years (big old guy on a big american scooter) and still every once in a while I just totally wipe out. debri on the road, a little pot hole I missed, a little patch of ice, a wet manhole cover it does not take much to dump you on your but even if you've "got the hang of it".