My major is mechanical design, manufacturing and automation, but I want to find a job as a HVAC engineer. Is it feasible? Is it difficult to learn?

Yes, I study materials, and I have to take an accounting exam for the postgraduate entrance examination. A science course and a liberal arts course may seem difficult, but it's not as difficult as you think.

To put it bluntly in college, what we learned was not professional knowledge. Under normal circumstances, the undergraduate course lasts for four years, the basic course lasts for two years, the specialized course lasts for one year and the internship lasts for one year. What knowledge can I learn? What really enables us to learn is not specific knowledge, but that we can quickly master his learning methods after we come into contact with new knowledge. This is why teachers in universities talk about more than ten pages in one class and such thick books in one semester, but some people still learn well. One method is universal and all methods are universal. Learning methods are mastered, and learning new knowledge is not a natural thing.

There will be difficulties. The hardest part is actually in the beginning Insist on everything, since you have decided, do it and stick to your choice.