Redesign UI/UX for mobile apps

We have a mobile apps application that has been used and running for almost 5 years now. The functionality is still good and okay, but we think that we need to refresh its look and feel for better experience for our clients & users. So actually you will will have to propose us a working xml layout files which will replace our current xml layout files. Our apps was built with Android Studio in android native Java & Kotlin. There are about 25-30 activity layout files to be replaced. Upon agreement of the contract, we will provide you our current layout files screenshoot.