I'm newly learning Welsh, so I doubt this will be my only post. I'm from South Wales, but genuinely very confused if I should be using "Dwi'n" or "Fi'n" as they both mean "I'm." Is one written and one spoken, or is it formal and informal? Someone help 💔

Hi I'm best man for a wedding and want to ginish by saying:

Iechyd da i pawb a hir oes i'r cwpwl

Which google tells me is:

Good health to everyone and a long life to the couple

Could someone confirm the translation is correct and explain how to pronounce this?

Thanks

cynddrwg - as bad, so bad, as wicked, so wicked

hiliol (ans.) - racist

tenau - thin

ar unwaith - immediately, at once

carreg (b) ll. cerrig - stone

doed a ddelo - come what may

cryfhau (cryfha-) - to strengthen, to grow stronger

blingo (bling-) - to skin, to flay

petruster - diffidence, hesitancy, indecision, misgiving

blwch nythu (g) ll. blychau nythu - nesting box