"Pedwar deg chwech"
Yes, it is a challenge to begin with with the two 'ch' sounds.
If you break it up into sounds you get:-
CH - WEH - CH
The 'ch' is the same as the end of Scottish 'loch'
This video series is great for pronunciation :- https://www.youtube.com/watch?v=16sqX2Baprg&list=PLz6oFM0_IszwxmU7dMcGQClZ5zMwX2EdY