Guten Tag Kreusslus.

If you are looking for knowledge I would say that this website has just about everything you will need to know. I wouldn't say parts are readily available but parts in the UK are easier to get.

"Oil Pump was removed", generally you'll need a bigger jet but I assume you know this already if you run pre mix already on all your bikes.

"Front Brake setup is missing" you can buy brembos from Japan but that's an expensive route, ask me how I know. Someone may have brakes for sale here.

This part of the website should help you a lot https://nsr-world.com/tuning/250-tuning/ignition/