Hi sorry to hear about this. I’m offline for most of today. I haven’t seen this error before. Try Googling the error, just take out the part of the URL that’s specific to your domain and leave in everything from /wp-admin/
You can also try updating WordPress via FTP or hosting file manager, that’ll replace all the files.
https://codex.wordpress.org/Upgrading_WordPress Please read carefully before proceeding as only certain folders and files must be uploaded. If you can take a hosting level backup before doing so, that’s ideal.