Yes that is because you are still using text and not value, you had the correct way in your original post text - Hello, I would like how can I put a value in my database.
It works perfectly for me here, just signup with any made up email address and password, then simply click on the button and your first name will appear in the top box with the same value being shown in the table as well which is taking its data from what has been added to the dataset itself.
https://givemeawhisky.wixsite.com/inserttest