HSBC bank europe doesn't acknowledge account

Hey guys I am new here I am dennis from italy. I am very sorry that my english is not very professional nor efficient.

Approximately 9 month ago I opened a bank account in HSBC spain to deposit all of my life savings and the gold and bracelet that i have been holding my entire life (they are sold) and some withdrawals from my mother's account and putting it into my with my mother's wish. It's total about 850,000.00 euros has been deposited into hsbc while explaining to the bank manager detailed to the bank manager of the BRANCH. And it is a savings account.

Now after 9 months passed I have gone into the bank to get a second reference letter for a company in china to send me items so with the reference letter i can confirm with thrust that i have the funds available and can be utilized by my wish to the company.( I got a reference letter from the bank before from the exact same branch with the signatures on it to show that I have available 850k funds in my account

And now i have gone into the branch and asked for another reference letter saying that i have enough money with the current date for proof for a new company that i have been talking to in china and singapore.They have said that THE ACCOUNT DOESN'T EXIST.Whenever I have shown them my passbook my account opening details account number and IBAN but they have said that the There is no recollection of that happening And i HAVE NO ACCOUNT WITH HSBC europe or spain.And they have accused me of falsifying and creating documents the Passbook and the reference letter that i was given before by them.And I have the hsbc key for online banking but it is logged out so it doesn't log into my account and when i try to log in to the hsbc on the internet it says the credentials are wrong.

after that they called the police and the police showed up saying ''I am tresspassing'' and then i have left the branch.Whenever i called them online they have said the same thing Saying the ACCOUNT DOESN'T EXIST and they have no account opening in my name in any HSBC branch AT ALL. 

The single deposit slip of 850.000 euros is in my hands but they looked at it and he tried to take it to the manager on the upper floor but i didn't allow him to take it without me since it is my only deposit slip evidence in case something happens and the manager came down looked at it for a second and called the police and I had to leave with all my documents in my hand without this drug bank acknowleding my account.

What are the steps to take in this situation ? I have talked to a lawyer and he says he has never seen any situation like this before.

How do i prove that i have an account with this bank and i want my 800k life savings back? Who is deciding if i ever have an account with this institution?