As part of your TME PhD journey, you will have to take graduate courses. Generally, you have to adhere to TME courses (requirements). That said, you have considerable freedom to choose Elective courses. With this, you can turn taking courses from a perhaps annoying obligation to an enjoyable part of your PhD life, helping you advance your knowledge and skills.
There are many different courses you can take (see Elective courses). In any case, you should discuss with your supervisor and examiner which courses you plan to take (e.g. as part of your ISP meeting).