There is no way for anyone to help if you can’t unlock (decrypt) your wallet for any reason.
If you don’t remember your passphrase, we can’t recover it for you. There’s no database (centralized or decentralized) where your private keys are saved.
If you type in the right password but the wallet tells you it’s wrong, double check your spelling. Try typing it in a text file (or anywhere you can see it clearly) and copy/paste it into the passphrase input field. There’s no way for the password to change by itself.