GCP WordPress Multisite Deployment

I already have a Google Cloud project up and running and one live WordPress site that now needs to become the first member of a new WordPress Multisite network. The end goal is a clean Multisite install on GCP that can comfortably host between six and ten individual sites, each served over Cloudflare-managed SSL with proper domain mapping.

Scope of work
• Spin up a fresh WordPress Multisite instance on my existing GCP project (Compute Engine or a comparable GCP-native option).
• Migrate my current standalone WordPress site into the new network without data loss, keeping all themes, plugins, and media intact.
• Add the remaining placeholder sites (I will supply domains) so the network totals 6-10 sites.
• Point DNS for each domain through Cloudflare, enable Full (strict) SSL, and confirm certificates propagate correctly.
• Map every domain to its respective sub-site so visitors reach the right content at the root URL.
• Harden the stack with the usual best-practice security tweaks and optimize for performance (e.g., caching plugin setup, Cloudflare rules, and basic GCP firewall rules).
• Hand over concise documentation covering login URLs, key config files, and a quick reference for adding new sites or domains later.

Acceptance criteria
1. All mapped domains load over HTTPS with no mixed-content warnings.
2. Existing site is fully functional inside Multisite (admin area, front-end, plugins).
3. Network admin dashboard lists 6–10 working sites, each reachable at its custom domain.
4. I receive a short PDF/markdown guide summarizing the configuration steps and how to reproduce them.

Please let me know your preferred method for accessing the GCP console and any additional information you need before we get started.