Seeking UI/UX Feedback for INCH-in-cm-umrechner.de – Improving Usability & User Retention

I would really appreciate your feedback on my project INCH-in-cm-umrechner.de. I’m currently trying to take this tool to the next level, and I feel like something is still missing—especially in terms of user retention, usability, and overall UX/UI clarity, even though the core functionality is alrea