Try this tutorial by Sajal
Here's the designer if you need it:
Use the example aia in the tutorial which works or try your own code using the Companion and test it. If your code works, it will run. 
If the code does not work, consider using the example model.
nights.text is empty, and empty is not something you can multiply.
This code works but whenever I transfer the data to the next screen
Whenever I test the app and the label becomes 0
Even if I put another number block such as 2. It still says 0 in the next screen
This code never populates the TinyDB1 Tag standard . 
Perhaps you mean hotelroom_lp.Selection = Standard
hotdelroom_lp.Elements will NEVER = Standard so your code always sets (stores) the Tag standard to 0 because the if condition is always false.
Do you have a TinyDB on Screen4.
