everyone is facing same problem... sometime it dont change properly.. do one thing buy a new cable or change the socket.. , and close all the apps running background ..
try once by changing charger or cable I used 3(or)4 galaxy's upto now the common thing I faced in all devices are after some days of usage they dont works perfectly on fast charging because the charger or cable are ruined try it by changing cable if it doesn't work take it to service center
