I am sorry you’re having trouble. The duplicate columns name problem suggests a previous migration could have been interrupted, leaving your database in an inconsistent state.
To resolve this I’d restore a previous backup that you know is working, then re-run the migration without interrupting it, watching out for any errors.
Alternatively, seeing MySQL/MariaDB as a backend database is deprecated, you might want to consider exporting your workflows and credentials using the CLI on this occasion. Then start n8n with a fresh PostgreSQL database and import workflows + credentials using the CLI.