Anyone know of a good online writing course?

I’m a writer.
I have an imagination that never dries out, yet my grammar, sentence structure and punctuation are shocking.
I studied writing at school, but, on turning 17 I auditioned for Drama School and never went back to writing.
Now as an ‘older,’ woman I’d like to get back into writing again and I find myself limited by my lack of academic know how – rather than an actual story.

Anyone know of a good writing course online to help me with all of the above!?

Thank you!