Shopify functionality complete, and speed optimization

I am looking for a Shopify expert to complete the functionality of my online store and optimize its speed.

Functionalities needed:
- Custom product options
- Step-by-step product order process

Speed optimization requirements:
- Improve page load time on both mobile and desktop versions

Timeline:
- The project needs to be completed within a week

Ideal skills and experience:
- Proficient in Shopify development and customization
- Experience in integrating payment gateways
- Knowledge of advanced search filters
- Expertise in optimizing website speed for both mobile and desktop platforms