Can't select single face

https://preview.redd.it/g5hnajc7636h1.png?width=1559&format=png&auto=webp&s=c83ec65c9af785b66b8e5f41fe40b21de6b36c7f

https://preview.redd.it/0nxfxlc7636h1.png?width=1524&format=png&auto=webp&s=6cb48b6c7dff3303e825ce32fe991240e9ce9b71

somehow I am not able to chose single face.., when I click over the face, it includes adjacent faces also in the helical drill as in the first screen shot.. What did I do wrong, how may I overcome the problem? I have wanted to apply 3 face blend operation, I was following a video tutorial on youtube