Robust GA4 Conversion Setup

My website runs on a custom-built PHP backend and I want Google Analytics 4 configured so every visit and meaningful action is captured in line with Google’s own best-practice guidelines.

Here is what I need from you:

• Create or refine the GA4 property, implement the tags (Google Tag Manager is fine if you prefer) and verify that all pages fire correctly.
• Map three key business actions—Purchases, Form submissions and Newsletter sign-ups—as GA4 conversions, then test each one until it fires once - and only once - per completion.
• Eliminate any risk of duplicates, gaps or mislabeled events so reported numbers can be trusted when I compare them with our backend.
• Surface traffic source data that clearly breaks out organic search, paid campaigns, social networks, referrals, direct visits and email marketing. I need to see this in standard GA4 reports without extra manual filtering.

Acceptance will be based on:
1. A live GA4 property that records real-time events during a screenshare walk-through.
2. Conversions appearing in DebugView and in the standard Conversions report after at least one full day of data.
3. Source/medium attribution visible for test visits generated from each channel.

If you know the nuances of GA4 event modeling and PHP-based sites, this should be straightforward. Looking forward to seeing accurate numbers at last.