4:35 is expressed as "five minutes and twenty to five". Why "five minutes and twenty" rather than "five and twenty minutes"?
That's got my
brian brain confused now. It's easier if you put the welsh words down for us to see them.

I think you're asking why "Pum
munud ar hugain i bedwar" rather than "Pum ar hugain
munud i bedwar"? (I've made the minute/munud in
bold to show its position)
I don't know the reason for why we say it like that, or for a lot of things we say in any language.
The way I think of it is that the descriptive bit (adjectives, adverbs) in Welsh comes after the important bit. So the sooner we get the word "munud" (minute) into the expression the better.
The more traditional way of saying numbers that I waffled about above is the way we say the time, but throwing in the "munud" earlier for good measure.
As far as speaking Welsh, it does help to try to speak it out to yourself as you read it. Many of the way things are said (or the spelling with the 'mutations') is to do with how it flows as it's spoken. That's wy my Welsh isn't as good as it should be because I live in England and don't have the chance to use it.
Trystan
PS I did manage to speak in Welsh to HM Revenue & Customs yesterday though - they have a Welsh language option. They answered the phone quickly and a lady spoke to me in perfectly brilliant Gog Welsh, and she sorted things out in a jiffy in a real friendly manner.