solve urgent error in VPS server Plesk

I was working on my server plesk downloaded some backup copies of one of my websites and derepente the server stopped working and was blocked. I have tried to restart the VPS server but now I can not access Plesk and any of my websites that I have hosted on the plesk server. When I try to enter the plesk server I get the following error: ERROR: PleskDBException: Unable to connect to database: mysql_connect(): No such file or directory /var/lib/mysql/[login to view URL] (Error code: 2002). Please check that database server is started and accessible. ([login to view URL]) I have found a possible solution to the error through technical support of plesk but I need someone who has knowledge to access the server via SSH or who has knowledge to restart the server in Rescue mode and solve the error and can return to access the server and my websites as soon as possible. Before the server error was almost full so I was downloading backup copies on my computer to free up space. I have found this solution to the error: [login to view URL] but I need someone who has knowledge to carry it out and solve the error because I have to not do it well and lose information. Please only offer people who are very clear about the work and what needs to be done