I’ve started learning UML but it confuses me sometimes (for example what i’m allowed or not to put in my USECASE diagram, last time i was wondering if logging in can be used in usecase diagram). Anyways i’ve made simple usecase diagram of e-learning platform, like lynda but you have to pay for individual course you’d like to take. Any suggestions/corrections about my diagram? (i’d like to bring more usecases into it)

I would split that Usecase called
Register/Logininto two separate Usecases. I think these steps are two separate actions and need different steps to execute. This way you are also able to transform the Usecases to Composites.We often do it this way:
Then you could add more detailed steps on how to implement/execute the certain Usecase in the Activity Diagram.
This answer is specific to Enterprise Architect of course.