We need templates for our mobile apps by modifying the CSS in our app engine

General information for the website: we provide online ordering and reservations for the hospitality industry
Description of requirements/features: Hi! We are looking for someone to use CSS within our App Engine to modernize the look and feel of our front end. We will provide you with access to our App Engine where you will find full access to the CSS to make modifications . We initially need a theme that will be able to be used for all types of restaurants but if we like what we see, we will hope to use you again for more custom templates such as ones for pizza, chinese and mexican restaurant themes. Please see attached pictures of current modern restaurant chain's apps. We would like for this project to be completed within one week of accepting the offer. Thanks and look forward to hearing from you!
Extra notes: Please see below some crisp, modern examples of how I'd like the app to look.