Hi, welcome to the forum! For free courses on content writing, copywriting, and social media marketing, I'd recommend starting with these:
HubSpot Academy: They offer great courses on content marketing and social media strategy.
Copyblogger: Their blog is packed with tips and free resources for copywriting and content creation.
Google Digital Garage: Check out their free courses on digital marketing basics which cover social media.
Udemy/Coursera: Often have free courses or trials on writing and marketing keep an eye out for promotions.
These should give you a solid foundation without having to spend a dime. Best of luck leveling up your skills!