Help! User ID storing for only a short time

Please I have a major issue, I am working on app and I set up the sign up using firebase because. I also used firebase to set up the user details, i.e to save their username and image. However, after logging in for a while, the app variable user ID becomes empty. I confirmed this by setting a label to show the user ID and nothing displays. This really affects the app, because when I try to update a profile details in firebase, all the previous data by other users clear, and instead of showing Users/app variable UserID/ Image or username structure, it clears everything and just shows User/ Image and username.

I have attached some screenshots below, your help will be highly appreciated, thank you.

I’m not sure but I think you have to use the set property instead the create object, or the create object with all the fields and not only the 2 you want to update.
Show your database tree. Pay attention also about what you are saving inside stored username and image

Thank you for your reply.
I have actually changed it to set property

and changed my database tree to userid/image or username, but it’s still the same.

I don’t know if this error could be as a result of logging in to the same account on different devices, cause I am logged in as a user on my laptop and also in the thunkable live app with the same user details, maybe this affects the app variable userid.