You can find the online course catalogue here. Before arriving you can read the course descriptions. It is not necessary to register on the website because after acceptance you will be placed in the courses you would like when you come to campus.
Please note: The faculties do not always enter all the courses taught in English into the online course catalogue. Be sure to ask your advisor at your faculty which courses they offer in English.
A course catalogue with descriptions about the course (“kommentiertes Vorlesungsverzeichnis”) is available from the “Fachschaft”, which are the student representatives of each respective study program. You may go to their meeting point and pick it up there. Additionally, you may purchase it at Skriptenverkauf, which is the office of academic printing.
A list of all the degree courses taught in English at TU Dortmund University can be found here.