How to re-connect WP files in lampp/htdocs to new SQL database to recover site under development

First time here, facing a bigtime wordpress situation. My Ubuntu installation crashed beyond repair during upgrading version. Managed only to copy the wordpress files, installed in /opt/lampp/htdocs, cause I’m developing in localjost.
There was no salvage of mySQL directory in Ubuntu installation, as it was beyond my skills in cli-linux, so it is gone for good…

What have tried so far, is creating a new database with same name as the old one, and copied wp-config.php and all files to the folder where reinstalled wordpress. I get “Error Establishing a Database Connection”.

Is there anything to be done, e.g recreating database with same name in mySQL to link wp-config or wp-content, and link WordPress file folder to new database?
Furthermore, if it is possible to link wp files to a new database,how to access site with all passwords lost?

Please inform me, before starting over the development of the site.