I'm a 1st sem master's student at ASU and worked as a Software Test Engineer, eager to learn more. What should I do?

Hello,
Thank you for your question and I apologize for my late reply.
First of all, congratulations on your decision to extend your studies to the postgraduate level. I believe that your choice will give you many supplies in your future professional life.
As you have already understood, there are various sources of learning related to your type of work. The 2 most basic ones are your postgraduate program and your work environment. Through these 2 you can continuously expand your work background, getting to build very good skills. It is also noted that experience through daily work is also a very good source of knowledge.
After that, you can use online trainings if you want to delve into a more specific topic. For example, if you learn something in your master's program at a general level and are interested in learning more, there are many courses available online.
Moreover, another important source of learning is books. For example, there are books specifically for Linux or for a coding language.
Finally I will advise you, always set your priorities and try to learn things that you think you will need.