If you fancy improving your skills with some free online courses, do have a look at Coursera. They offer video lessons from lecturers at universities & colleges around the world; you’re assessed by answering quizzes & submitting assignments. There’s no need to pay for the certificates (which are meaningless, as they aren’t recognised qualfications), just enjoy learning & enhancing your skills.
They cover a huge variety of subjects and have some very interesting music topics. A six-week Songwriting course has just started if you’re interested & quick off the mark (or you can opt to be informed when the future sessions are held). Others currently available or in the pipeline include music theory; history of western music; classical music; history of rock; appreciations of The Beatles & Rolling Stones; the American South (which includes roots music & the blues); world music; rehearsing musical ensembles; musical sounds/electronics & several more.