Headless CMS Integration for Next.js

My site, www.theagilenest.com, is built with Next.js and I’m ready to separate content from code by moving everything into a headless CMS. I want to keep the front-end exactly as it is and simply feed it richer, more easily editable data... (Budget: $30 - $250 NZD, Jobs: API, CMS, HTML, JavaScript, MySQL, Next.js, PHP, Web Development)