Installation plan needed but have not yet found a perfect kitchen

Experts should be able to make something of that. Apart from that, the floor plan should also be available,

That should be something professionals can work with. Apart from that, the floor plan should also be available,

Yes, I also think they can make use of it. There will probably be a floor plan at the kitchen store, but not without a contract.

It's really not that difficult to draw up your kitchen space and mark all the measurements of the cabinets in the plan. They are standardized in width, and the distance from the row to the island can be measured by yourself from various walk-throughs in furniture stores (it doesn't hurt to try out whether you like the distance). The heights for the oven and co can also be determined reasonably well this way. It just requires some time and commitment.

Have you perhaps already offered the kitchen studio to pay in advance for the plan with exact positioning for the oven etc.? 200 to 300 euros, which will then be credited upon kitchen purchase?

You only need to set the line spacing. Provide a dimensioned floor plan, and the plumber will then be able to plan the water and wastewater connections based on the kitchen plan. Same for the stove socket on the wall. The dishwasher will be located in the island and also requires a socket on the wall (separately fused); the cable can then be routed in the plinth area. Additionally, two sockets (separately fused) for lighting and possibly recessed sockets on the countertop.

The sockets on the HS wall are a no-brainer. The cabinet grid dimension is 60 cm, all three visible appliances plus the refrigerator are separately fused and receive a socket 20 to 80 cm below the bottom edge, the refrigerator also above. Additionally, at least one more socket for general use such as drawer lighting or a multi-cutter at 30 cm in the middle. Better to have three, then distributed at 30 cm height.

Is the cooktop really sitting tightly against the wall? How are you supposed to cook properly there, or where do you want to put your left elbow?