Resolve Gmail Spam Filter Issue

I am sending emails from Gmail, but most of my emails are landing in the Spam folder instead of the Inbox.

Requirements:

1. Check and fix email deliverability issues.
2. Set up proper email authentication:

* SPF
* DKIM
* DMARC
3. Configure a professional email sending setup.
4. Improve sender reputation and inbox placement.
5. Ensure emails are delivered to the Primary Inbox instead of Spam.
6. Test deliverability across Gmail and other major email providers.
7. Provide a complete report of changes made and recommendations for future email campaigns.

Goal:
Emails should reach recipients' inboxes with the highest possible deliverability rate and avoid spam folders.

Please share your experience, previous results, and estimated timeline for completing this project.