I think the best place to start is by getting your hands dirty with a real deal API. https://learnopengl.com/ is a great place for that. Oh and the best part is that the book is FREE.
You'll need to be comfortable with C++, but even without in-depth knowledge of the language, the tutorial takes you quite far.
https://learnopengl.com/ is a super popular recommendation, but I found it a bit lacking when trying to understand how things work. I tried using a college book instead, Computer Graphics Programming in OpenGL with C++ and found it more approachable.
Hot take: OpenGL is lacking when trying to understand how things work. OpenGL hides a lot of state from the API because it has a lot of cruft from when Graphics cards were ASICs. DirectX 11 and especially 12 and Vulkan are closer to the actual hardware capabilities of the GPU and state is more explicitly passed between stages rather than having a state machine hiding somewhere in the driver
You'll need to be comfortable with C++, but even without in-depth knowledge of the language, the tutorial takes you quite far.