Subsequent guarantee

Good day to each other, the following problem: I bought a used Astra a few days ago. A look at the FOH shortly after the purchase showed that the car is also ok from “below”. But: The steering gear is defective. No problem I think, is a case for the warranty. But the dealer wants to (or has already) with my data a later guarantee, which I will get soon. I could then have the damage repaired and the FOH then has to get in touch with the warranty company. Is this all clean and correct or should I leave my hands on it and take the dealer into the warranty obligation? Greetings, Andreas