Modern UI/UX Design for Web App

I'm looking for a UI/UX designer who can help me create a modern and minimalistic design for my web app. The primary goal of the app is to engage users, with a key focus on optimizing sign-ups.

Key Requirements:
- Expertise in UI/UX design, particularly for web applications
- Ability to create a modern, minimalistic design
- Proven experience in designing for user engagement and optimizing sign-ups
- Strong portfolio demonstrating successful past projects
- Excellent communication skills to understand and incorporate feedback