I definitely agree with Emma, I started doing 4 A levels for the first few weeks to choose which to drop. I took German A level as one of my subjects.
It is in my experience quite difficult and a lot of work because you are not only learning the language but you learn history of Germany, for example in my exam board (Edexcel) you learn about East and West Germany and the events leading up to the reunification of Germany. It's very interesting and, in my view, widens your perspective of current world issues and events. If you like history then you will really enjoy German.
Another thing you do more of is grammar, which gets surprisingly easier throughout the course. I was not good at grammar at all in GCSE but the language is much more accessible now I have a firmer knowledge of the different cases etc.
In the exams themselves you will do two essays (around 350 words each); one essay will be about a German book you will read and the other is about a German film you watch. The book can be a play if you choose. I believe you can do two pieces of literature if you choose instead of a book and film but you cannot do two films. You do the listening and reading exam which is similar to GCSE paper. There is a translation into English and a translation into German.
In the speaking exam, you have to discuss the topics you learn but there is also a section in which you talk about your IRP (independent research project) in which you have prepared and researched a topic. This can be anything that interests you that link to German - A German singer, or sports team, event etc.
Something I did which helped with the speaking exam for the topic areas (and also with the other exams in general) was make mind-maps with words and phrases you can learn to give you a starting point and points to include or steer the conversation to. I'd definitely recommend doing this if you take German.
I hope this hasn't been too overwhelming but I was super confused about what was actually involved in the course and exam for ages so I hope it helps. This is also my experience which has been with the Edexcel exam board. The course may be very different in other exam boards so check which board you would be doing.
Please ask if you have any more questions