Learning the operating system is really painful for me

Because I'm about to graduate, I joined a company for internship. I only used single-chip microcomputer to run bare metal in the school and didn't use the operating system, but the people in the company programmed under the Linux operating system. I had to start learning Linux, but I've been learning Linux for several days, but it's still very difficult. I can't understand it and feel very uncomfortable. I don't know how to learn.So I hope to seek some help online.