several keyboards are not woking

this is extremely frustrating and I am writing this on an external keyboard. My internal keyboard has several letters that need to be pressed multiple times before they decide to appear on the screen. ‘R’ ‘T’ ‘Y’ ‘U’ ‘I’ ‘O’ I’m a writer so you could imagine how I’m slowly losing my mind. I did clean these keys by removing the key and then cleaning out the gunk underneath (without an air dust) and when I fixed it back up, nothing has changed (granted some keys take shorter time to respond than before). Please PLEASE help me out.