Hello!
You should take a look at SEO (search engine optimization) courses.
Coursera has quite a few of them, as well as a specialization that group 6 of them:
- Introduction to Search Engine Optimization
- Search Engine Optimization Fundamentals
- Optimizing a Website for Search
- Advanced Content and Social Tactics to Optimize SEO
- Advanced Search Engine Optimization Strategies
- Website Optimization Client Report Project
I haven’t tried the course myself but the reviews seem very positive. The lowest average score is 4.5/5.0.
Generally, specialization in Coursera are not free, but the single courses, if you manage to find them, can be audited without spending a cent (or whatever is the lowest coin where you live 
).
But be aware that by auditing you won’t receive a certificate nor you’ll be able to do the end of the week projects.