Any good recommendation if I would like to learn digital marketing?

HI.I have a question and tks for your ideas first.

I started my digital marketing journey about 2 years ago when a pandemic happened.I first worked as an influencer marketing and I did some Facebook ads before. Then when I joined this company, I became a branding manager doing Shopify selling products. We have a team of SEO and google ads to manage the business. But I would like to learn digital marketing systemically and in the future when I run a new brand or new business, I could know exactly what I should do and where I should start.

If you had a good recommendation, please let me know. What kind of free digital course I should go to in 2022. Paid one is cool too but within budget of $300.tks