keyboard problem multiple words one key

my keyboard don´t t work well

if i push the key "S" appers two words "gs" the same with the keys "2" 25 "w" tw "x" bx and "esc" ''''''''''

any idea¿ i open the keyboard viewer and when i push the key i can see how the two keys are displayed at the same time just wihit one key. it happens affter a mactune (program) maintenence, i think must to be of the maping or preferences. what do you think¿