Error Establish Data base connect issue please urgent help needed

Hai everyone please help urgent solution needed… I am using Digital Ocen 5$ Droplets. Actually my disk full 100%… So one of my website showing error “Data base error”. And now I m deleted some temp files using filezila and DO plan increased… One website working but page not working… I checked wp-conf.php file also everything is crct still i don’t have what happend and

2nd website totally error… Please anyone help me