"Dw i'n" (or the non-shortened version "Dw i yn" is used in front of a verb to say you are doing something. Examples: "Dw i'n mynd" = "I am going" or "I go". "Dw i'n hoffi" = "I like" or "I am liking".
I am Welsh and it should be ydw I not dw I because you say dw I ddim yn hoffi pêl droed (which means I don't like football) dw I means I but ydw I is I am