The template apps provided by Microsoft are good for demonstrating the capabilities of Power Apps, but they aren't well-suited to be a person's first experience modifying/constructing their own app. To make these apps work in your own org, you generally need to connect them to a data source that does functional things, such as populate the question collection.
If you are looking for a quick/easy way to do an employee survey, I recommend Microsoft Forms. It automatically saves survey responses into an Excel file that you can download.
If you want to go down the road of modifying this app to work in your org, here are three references to read first so you can get up to speed faster:
Then, as you develop specific questions, do a search on the forum or post your question.
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