Glitched my computer

This is the worst app ever. it is now glitched and screwing up my computer. it doesnt say its open, but its open and wont stop playing. I went to force quit option in apple bar and it doesnt say its open, if i click command q nothing happens. I have restarted and cliked do not open previous windows, i have turned off, but it wont shut off and it wont let me quit it and it doesnt say its open!!!! I cant delete the app because it says it is open, however it is not. I have tried everything in the books!!!!!! DONT BUY THIS APP
if anyone has any advice that would be great etc!! thanks

person1097563 about Screen Snake