(Beginner here) In English, we would say "I am (verb)ing", Welsh does the same, but of course we don't usually say "I am liking", however it is a similar format. (And you could say "I am liking this coffee" for example, so maybe it sounds less weird in some cases? I digress! )
In order to link "am" and "to like", they add a special word that doesn't happen in English. "dw i'n hoffi" Here it is the apostrophe+N. This can be easily pronounced like "een".
However, if you want to say you Don't like something, as in the above sentence, it would be hard to say "dw i ddim'n" so instead of apostrophe+N, they put a 'y' in front of it and make it it's own word. "dw i ddim yn hoffi"
In my head when I translate to english, at least in the beginning, I kind of say "No, I do not 'link' like swimming", if I need a mental reminder that it needs to go there.
If you are using a computer there are little explanations/tips below where you select to start a lesson. If you're on a phone they aren't listed. I didn't know this for a while, and once I found out, things got so much easier.