Don’t doubt your ability, Kathryn - you can speak English, so you can speak Welsh - it’s the same neurological journey. There is no doubt at all about your ability to do it.
The old lessons 6 are pretty tough - badly written, I’m afraid - sorry! If you want to carry on with Course 1, then just press on through them and it will eventually bed in as you carry on progressing - but I would certainly recommend that you switch over to the much better written Level 1 