Email marketing specialist to solve deliverability issues and strategize a campaign of 12 emails

My Deliverability dropped from 30%+ in 2024 when I also owned a gym to 2% iow after selling it and going quiet for a year before marketing my movement center. My own email campaign from my own email warned me I might be an impostor. I've contacted Mailchimp and Godaddy but the problem seems to persist. I'm a small business that can't afford to lose more of my only 3800 email contacts. I'm considering buying a local list of about 7000 - starting over. I recognize the dangers but it couldn't be worse than 2% Contact me if you KNOW how to fix deliverability and then we can design a dozen emails that match my branding. I have a list of subjects but we can brainstorm and develop a plan together. I'd like an automated campaign, ready to go with a dozen emails to start.