Well done for having a go Jen.
Gobeithio = to hope, so you need dymuno (to wish) instead. You could either say “dwi’n dymuno” (I am wishing), or use the short form dymunaf (I wish).
Os na fyddwch chi’n llwyddo i ddechrau,
Ceisiwch, ceisiwch eto
The last two lines are a literal translation, but in Welsh we have a different idiom for “If at first you don’t succeed, try, try again” which is “Dyfal donc a dyrr y garreg”, so you could use that instead if you wanted.
PS - nice beats on the video!