You see all the lessons in which your entire class participates, but lessons in which the class is separated (languages, sports, crafts, etc.) are not shown?
In this case, you probably were not assigned to all lessons and therefore do not see all the lessons relevant to you under "My timetable".
The respective allocation falls under the responsibility of your school, please contact your school's WebUntis administrator. For data protection reasons, we (Untis GmbH) are unfortunately not able to assist here.
As soon as your school has provided you with access, please select your class in the menu under "Timetables" - "Classes". This should allow you to view the class timetable.