When it comes to choosing a CMS for an App-based website, there are several features that must be taken into account:
1. Mobile responsive templates
2. Powerful but user-friendly drag-and-drop editor
3. Apps that work well on mobile interfaces
4. Mobile eCommerce options
Actually, there is a great number of mobile web design software that allow developing a website exclusively from a mobile phone. You can run the software on your smartphone and immediately start creating your website. I personally prefer working with mobile website builders
https://www.webbuildersguide.com/best-website-builder/mobile/. Due to their simplicity and a wide range of options, it is easy to make apps, even if you don't have coding skills and experience.