Modify shopify store, SEO

I am looking for a Shopify expert to help me modify my store and improve its performance. I am open to suggestions for a theme and have a preference for a modern and clean design. Including organizing products in categories, SEO, and of course a mobile friendly design. The modifications need to be completed within 1 week.

Skills and experience needed:
- Strong expertise in Shopify and its customization options
- Experience in improving site performance and optimizing load times
- Ability to suggest and implement design changes to enhance user experience
- Knowledge of responsive design and mobile optimization
- Attention to detail and ability to meet tight deadlines.