Creating web app in same laravel project as API

I am working off of a laravel 5.6-powered API created by someone else which serves as the backend for an iOS app. I would like to work on making a web app that utilizes data from the API's connected database, models, and controllers. I am struggling to figure out how I can best achieve this without creating massive problems in the future. Part of the complication is that the API also has a frontend interface (api.example.com/admin) to monitor data, so I don't want to run into disorganized and incorrectly pointed views, controllers, etc. In addition, my APP_URL is api.example.com and I want the web app to live on example.com, and I'm afraid that changing the APP_URL and other configurations to accommodate the new subdomain would cause issues. I am still somewhat of a beginner with web development and laravel and would greatly appreciate some feedback here.

Would it be advisable to start this web app on a separate project or to have them on the same project? How would I handle/organize routing and views as well as controllers? What sorts of configurations would be necessary to have them on the same project?