Who will

Question

I've been in this app for 4 months, who can teach me much in app development

Answer 1

This is a self-learning platform, if you want to that some person teach you then you can join any tution/institute.

Answer 2

I think you could try an app developement video on youtube, there are many to choose from.
https://www.youtube.com/results?search_query=app+development+for+beginners
Coursera is very good.
https://www.coursera.org/specializations/android-app-development?
Udemy offers courses that are very detailed but they aren't free.
https://www.udemy.com/courses/search/?q=android+app+development&src=sac&kw=app+devel

You may all so search the web to find other courses.

Answer 3

Just by searching the forum and the community tab, there's a lot to learn.