Alchemy Abstraction Account SDK in Java troubles

[swag-eag]

Hi.
I am trying to use the Alchemy Abstraction Account SDK in Java...
But I am having troubles...
I am starting with eth_estimateUserOperationGas and the example does not work... I put all the parameters by default in https://docs.alchemy.com/reference/eth-estimateuseroperationgas and I get an error message:

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32602,
    "message": "Invalid user operation for entry point: 0x5ff137d4b0fdcd49dca30c7cf57e578a026d2789"
  }
}

Then I try with a token smart contract to know the Gas to make a ERC20 transfer... I got the callData from Web3j (ABI wrapped)... I use my API Key and the dummy signature: 0x00fffffffffffffffffffffffffffffff0000000000000000000000000000000007aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1c
And I got errors.... about 0G... AA23 reverted
How can I send fee coins to the default Paymaster: 0x9db7f05b0eb93eb242b5913596dcfaada756af5c ?... Or how can I create a new Paymaster?
Should I sign the signature field (for other UserOperations) with https://api.g.alchemy.com/signer/v1/sign-payload as explained in https://docs.alchemy.com/reference/signmessage with a Bearer API_KEY?... Or is there another way?
I do not find a way to go on...
Thanks.