Help to build the Android App

Hello! So, I just buy these product - [login to view URL], the seller sad that I just need to change the url of my website and change the App name to publish it to Play Market and give me the product. So, I do all this and now I have some problems with it: 1. When I run my website in smartphone browser - it's work very well, when I would like to run my website into these app - it's not working or working very slowly on my Galaxy note 8. I look the log of my webserver - here the data connection is ok, but the screen on my app it empty. 2. I need to preload the logo image when the App runs the first time - I choose these product for this - [login to view URL], but the seller of the app sad that I may use this product - [login to view URL] . 3. I make the Signet APK - but when the build run - in the end of process it's write - Connection timed out: connect , but I do all which the instruction sad, and rename my app - [login to view URL] . But it's not working and have errors. So, what I need: 1. I need to make the my App, which will no have these problems and works fast, not slowly, and may upload my app to Play Market with my app name. 2. I need all codes and the information-instruction for me where I do wrong, when I build my app. Thanks