One Backend for a Website and for Mobile apps

We want to build a website and IOS/Android mobile application from scartch, the app and the website should access and manipulate data from a same database

We Planed to build a RESTful API using laravel framwork(which we have little knlowledge about), so that both the web and apps can interact with the database

But We have lot's of dought

1-REST APIs are exposed as an HTTP Services

2-Sometimes an UI action would require you to manipulate the data structure or multiple REST calls to create the resulting view

3-Direct one-to-one mapping of UI action to backend REST calls may not be possible

The app we are gona build is an E-comerce app

So What is the best solution or development procedure to achive this

Thank You