Because Welsh is Verb-Subject-Object you need a link word for additional 'verbs' in the sentence.

Dw i = I am Hoffi = to like/liking

Dw i + yn + hoffi = Dw i yn hoffi (contract to 'Dw i'n hoffi) = I am liking rice/I like rice

We put 'ddim' after the 'I am' to make the negative.

Dw i ddim yn hoffi reis = I am not liking rice/I do not like rice

The first example here may help - https://www.duolingo.com/comment/13844144 - where yn is used to link the verb 'to be' (dw i, etc) to an uncompleted action.

SAME I KNOW HOW YOU FEEL :D I HATE WRITING SUCH LIES LIKE THIS