I had great difficulty with challenge 13 as I couldn’t work out the pattern (and don’t know what it looks like written down, which I find can help).
“She’d better try…” sounded like “well i hi drio” which makes sense. But then I’d expect “He’d better practice” to be “well i fe ymarfer”, but it just sounded like “well something ymarfer”. The something seemed quite long, and nothing like the word for “he” that I’m used to, and no matter how many times I listened, I couldn’t make it out.
Then for the past tense, “she wanted to” sounded like “othin moyn”, but “he wanted to” was “boven moyn” and “the old man wanted” sounded like “ova hen dyn yn moyn”. I just can’t get the pattern here!