High power connection for IKEA stove and oven. Please advise

The standard wiring is green/yellow for the ground conductor and blue for the neutral conductor. The rest are phases. Why is the wall connection a cable, and why are they stranded wires? For that, you need ferrules matching the cross-section, or corresponding clamps (e.g., Wago 222).

If you have properly secured it, nothing should happen. But if you don't even know the cable wiring, I would at least get someone who knows what they are doing. The connection cable must definitely be tested in the junction box. Accidents happen when two people mess things up together. Trust is good, control is better.

Only have it done by a professional

Unfortunately, I am an absolute layman when it comes to 230V connections and don't want to destroy my electrical circuit.

Hello,

the combination "absolute layman" + 230V does not sound good.
Better to listen to the suggestions and spend the 20 euros.
Destroying the electrical circuit would be the lesser evil compared to what could happen.

Best regards