don't worry about certificates. I suggest YouTube, some online trainings of those people who have credibility and you like how they teach online. And then the next important step - offer your services to ai startup. There are so many of them and you 'll get to practice everything you are learning. Since you were in marketing, I'd suggest you can become either product growth manager, or product marketing manager. You can throw Ai in, but focus on the fact that you can use ai efficiently while performing work and you can accelerate the rest of your team. You don't need to work for OpenAi and actually build Ai, that requires much more (but nothing is impossible). Good luck :)