Bank does not accept own contribution

No, why should that be the architect's task, you want to do everything yourself and believe that you can do it properly. You are the client and therefore responsible for everything yourself.

I would rather not leave the bank half in the dark, but look for a bank with which you discuss everything openly and honestly beforehand. It’s about too much money for you to "play dumb," and the banks are not stupid either. They want to see the invoices afterwards for what you previously stated. With us, you also had to explicitly indicate which trades were to be done by yourself and which by professional companies. We also had to specify afterwards for the building insurance which trades were carried out and by whom. That is the next topic, by the way.

An architect is not someone who has detailed knowledge of all trades down to the smallest detail.
Do you think he will sign for the bank or whoever that everything was carried out without defects if you installed it as a layperson without any guarantee? He at least has to bring in experts and specialists himself.