El Capitan won't let me downgrade

el capitan ruined my computer. I decided to shut it down for a bit wait for an update. Updated today now it won't do anything past this screen

my Mac ran perfectly fine before this crap update and I can't afford a new computer so I'm reasonably ticked off. What do I do? I tried command r but nothing happens. Don't recommend that. literallt sat here and waited 15 mins holding the keys with no response.