MySQL error

Hi, I am getting this error. And now my sites are closed.
http://prntscr.com/dn956q
I updated mysql, but the sites are not open.
I want to get sql backup and it gives such an error.

mysqldump: Got error: 1045: Access denied for user 'user_HHyGtR'@'localhost' (using password: YES) when trying to conn                    ect

What should I do in this situation ?
thank you.

check mysql log file

cd /var/lib/mysql/
and after delete this:  rm -rf tc.log
after:  service mysqld restart

cd /var/lib/mysql/
and after delete this:  rm -rf tc.log
after:  service mysqld restart

this is one of the reason but not everyone have the same issue.