Wish: Make iOS push notification text (copy) less obnoxious
The iOS notifications read like they were written to motivate 7-year-olds. While I'm sure Yousician's userbase includes many 7-year-olds, it also includes people who simply want a friendly, informative notification, not clickbait.
At a minimum, if you aren't willing to get rid of the gamified clickbait garbage, then at least adapt the notification to someone's progress. If someone's past the first few levels and/or you have reason to believe they're an adult, generate notification copy that doesn't feel like it was written to cajole a small child.

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Alfonso commented
SpanishDict does a decent job of this. Their notifications are engaging and motivating, yet don't talk down to their users. Here's two representative examples:
"Keep your 4 day streak going. Here's 14 new vocabulary words."
"You have 17 words up for review. Dive into a quiz."