I just noticed that when I am making an app, the background image, graphics, fonts or even the shapes do not adjust well on all device screens.
I saw a tutorial that uses the screen height property to adjust components.
Does anyone have a responsive app that I can look at so I will some idea on how to make a good app that does not get destroyed at different devices. Also maybe a general tutorial on how to get started for a good app with great UI.
I would just like to have an idea on how everyone starts their apps and even on how they do it because I feel like I am making my app wrong and would like to look into great apps aia files 
and no, I am not interested into selling apps but I just want to make a personal app.
Thank you for all the help!
I am a web developer using js and new to app dev. 