Study and development documentation for the new app and website.

Description

I like to develop mobile apps for platforms such as Android, Apple, and Huawei. I also like to develop websites that work along similar lines to apps, providing an experience that operates and processes in 90 to 95% of the same style on both the app and the site.
I need to research similar apps and websites of competitors to identify all their features and would appreciate your suggestions. I will compile my insights into a comprehensive document that will serve as a blueprint for developers. This document will help them study and develop the app and website based on current app popularity by city and country.
It is essential to understand study apps and websites, as well as how to create detailed documentation for developers. Additionally, consider providing valuable suggestions for long-term improvements, along with marketing strategies to be included in a separate section after development.