Starting solids- HELP!!


I need any and all tips on starting solid foods! I am TERRIFIED. My 9 month old has been exclusivley eating purées (and formula of course) since 6 months and I know it’s time to branch out and try solid foods, but I cannot stop thinking about him choking. How do I know he’s getting enough? How much should I prepare for him? Do I still do purées in addition to more solid options? How much formula should he be eating in a day in addition to his solids? I am spiraling 🌀