Mobile App UX Overhaul -- 2

I have a fully-built mobile app that functions reliably, yet the overall flow and visual language still feel clunky to users. My sole focus for this engagement is to improve the user experience from the first tap through to checkout, bringing the interface up to modern usability standards.

Here is what I need:
• A critical review of the current screens, identifying pain points and missed opportunities.
• A clear UX improvement plan supported by low- or mid-fidelity wireframes that illustrate revised navigation, hierarchy, and interaction patterns.
• Optional but welcome: quick interactive prototypes (Figma or similar) so stakeholders can test the new flow before development begins.

When you reply, attach a detailed project proposal outlining your approach, preferred UX tools, estimated timeline, and how you will measure success post-launch. High-level résumés are less important to me than a step-by-step plan I can evaluate.

The app is already on iOS and Android, so recommendations must account for both platforms and follow their respective design guidelines. All design files must be delivered in editable format (Figma, Sketch, or XD), together with any style guides you create.

Questions welcome before you craft your proposal.