Now i have only one question to maybe find a solution :
Can i recover seed from a list of private keys ?
No, this does not work.
It is not possible to calculate the seed (or the mnemonic code) out of one or multiple private keys.
The child-private-key-derivation function does use HMAC-SHA512. The only option would be to
bruteforce it, which is practically not possible (2
256 is too large to bruteforce).