Shopify E-Commerce Store Build

My company is ready to launch an online store and I need it built on Shopify from the ground up. The immediate, non-negotiable requirement is a fully functional payment-gateway integration that lets customers check out smoothly and securely. I already have product information and branding assets prepared; what I need is the technical expertise to turn them into a polished, conversion-focused storefront.

Key expectations
• Customise or create a Shopify theme that matches our brand’s look and feel, optimised for mobile and desktop.
• Configure products, collections and basic SEO so items can be found easily.
• Set up and test at least two major payment gateways (for example Stripe and PayPal) with fraud-prevention settings in place.
• Ensure loading speed, responsive design and clean navigation.
• Provide a short hand-over guide so my team can manage inventory and fulfil orders after launch.

Nice-to-haves we may add in a later phase include product-review functionality and customer account log-ins, so coding with future scalability in mind is appreciated.

Please share relevant Shopify stores you have built, outline the tools or apps you prefer for payment integration, and give me an estimated timeline from kickoff to go-live.