Application Instantiation Error! after Template install - Joomla! Forum - community, help and support

hi there,

i new joomla, have basic knowledge web development , linux administration. problem:

joomla freshly set , working, wanted nicer template, downloaded one: https://www.gavick.com/download/joomla-themes/meet-gavern
and seems intentionally or accidentely crashed complete thing. if try access either website or administration site, shows:

error displaying error page: application instantiation error: not connect mysql.

ok, real problem: found several threads error, server not mine , before bother owner ssh-access, want know: likely, need root-permissions , have idea whether happened malicious intent (and if yes: can securely trusted templates)?

and finally: hope correct forum this. if not: sorry , please move correct one?

thank you!

ok, apparently somehow disappeared.

would interesting know, have happened, generally, can considered solved.

(in future test on own server first avoid situation)