Degree assignment Web Services - Implementation

I need help coding a web service for our assignment. The picture should be the assignment (the link at the bottom) and I do not really know how to code everything (writes in C #).

Register study results You must create a prototype for registration of study results via some form of user interface (Figure 1) in Canvas. The information required to register grades for one student in Ladok is; social security number, course code, module, date and grade. One module corresponds a given number of higher education credits on a course. The process starts with the user (examiner) entering the course code, after which the modules for selected course is read in list (Module in Ladok) and students including assessment of the course assignments is shown. The user selects the module and begins registration of examination dates and grades for each student. When the registration is complete, the information should be sent to Ladok, under In this process, the student's name must be replaced with the social security number of each student. If an error occurs when the data is saved in Ladok ex. if the specified module cannot be matched for one student, this shall be notified to the user.

enter image description here