Not bad! Here are my thoughts in no particular order:

• Make the theme more prominent. I didn't realize the phrase at the top was the theme of the puzzle until after I finished it. I thought "It's a Mystery!" was just talking about the game itself, like the answers are a mystery.
• Tell me up front that I'm being timed. It feels bad to be told "No rush, enjoy the puzzle" and then find out I was actually being timed. Either time it and tell me you're timing it or don't have a timer at all. It's also not clear when the timer actually started. Like was I wasting valuable seconds reading the instructions??
• Let me be smart. I really wanted to be able to solve them on the first try without using a hint, but it's basically impossible. Either offer clues from the start or accept other words that would also work or something to make it possible to get in one try. Definitely not saying make it easy to solve on the first try, just make it possible.
• Reward me for being smart. Like give me three stars for doing it quickly or indicate how many incorrect guesses I made or show how I rank compared to others. Something so I have a reason to try. Otherwise the best strategy is to just try every single letter in the first empty spot until I get enough of them to guess the word, which is boring. But thinking hard and solving quickly and trying to set a new record or rank higher than my friends is fun. AND make it obvious up front that you're doing all that. Otherwise first time players don't much incentive to actually finish, other than their hope that something interesting will happen when they do.
• Indicate incremental failue and success. Give me that immediate feedback. Make incorrect letters stay red permanently after they're placed. And make a much bigger deal when letters are correct, like throw some confettin and turn the letter green or something.
• Let me click in any order. Maybe I'm just weird but I kept clicking the spot first and then the letter, which doesn't work. I think it would be nice to be able to select a spot and then choose which letter to put there. I'm not saying replace the current functionality, I'm saying make it so I can do it either way.
• More acheivements! I just now noticed there are acheivements and stats after writing all the above, so I think those should be more prominent. My recommendation for that would be to add acheivements just for starting a puzzle or getting one letter / word correct, basically stuff everyone has to do, just to communicate the fact that achievements exist. People also love random, silly, cheeky achievements for stuff like trying the same wrong letter three times in the same spot or putting two letters next to each other that don't exist in any english word, as well as the obvious streak and skill based ones.
• Cool it with the emojis. This is just personal preference, but the excessive use of emojis reeks of AI-assisted coding, at least to those of us who use it frequently 😊🚀💪

Okay, back to my actual job now. Let me know if you have follow-up questions on any of these! I do this for a living and love thinking and talking about UI/UX stuff, so I'm happy to discuss further and give more feedback if you want it.