How many characters do you think are missing from your password?

You can recover that long password only if you know most of the parts of your password. There is a tool called BTCrecover that you can use to brute the wallet.dat file from your bitcoin core wallet. So make sure that you make 2 or 3 copies of the original wallet.dat file before you try to recover your wallet.

Please read the guide how to use the BTCrecover here https://btcrecover.readthedocs.io/