Answer 1

Android:
1) Learn java ot kotlin.
2)take these courses.
https://eu.udacity.com/course/new-android-fundamentals--ud851

https://eu.udacity.com/course/advanced-android-app-development--ud855

Web:
1) Learn: HTML and CSS.
2)Hire a server.
Buy a URL.
Point URL at server.
3) write the site anf upload it to the server.
4) Learn Javascript and modify the site with this knowledge.
5) understand Javascript libraries.
6) Learn php.
7) learn SQL.