In welsh it is perfectly acceptable to use english words whenever you don't know or can't be bothered to think of the correct welsh word. For beginners therefore welsh is the easiest language of all to speak as you only need to start off with one welsh word every now and then and yet you will still be regarded as a welsh speaker. You can then gradually increase up to the point where around half of your words are in welsh. More than that and people will think you are a welsh language extremist.
There is a cat in the garden. (English)
There is a cath in the garden. (Welsh language beginner)
Mae cath in the garden. (Welsh speaker)
Mae cath mewn y garden. (Welsh speaker verging on Welsh language extremist)
Mae cath mewn yr ardd. (Welsh language extremist)