Hello! You have to make a button to lead to the achievement gallery yourself - it's not built into your project or the tool because I don't know how your main menu screen is set up. That's what this bit of code in the instructions is for:
textbutton _("Achievements") action ShowMenu("achievement_gallery")
You need to add that or something similar to your project to access the achievement gallery. Don't delete datetime either - that was a very specific case where another bit of code had imported datetime already in a different way. I suggest not changing anything in the backend unless you understand what you're doing.