"Are you eating cheese?"
Translation:Dych chi'n bwyta caws?
Well mostly we just used "Dwi'n +verb" for both of them but there are present tense endings which can be added to verbs, i.e Rhedeg= To run, Rheda i=I run etc with different ending for each person. These do still exist but they are rarely used and I only know them because I asked my Welsh teacher in school.
Pretty much any sentence that uses a form of "bod" (dw/roeddwn etc) also takes a yn/i'n (but not the emphatice i.e "Ellis dw i" doesn't need an 'n at the end). A few exceptions are when using eisiau/isio and angen(need) these do not take yn/i'n . Also if the sentences contains wedi the yn/i'n is not used. I'm sure there are other rules, but you should just pick them up as you go along.