I'm doing AQA AS German and i've got my oral exam coming up in about 5 weeks. Don't know if this will help but I am preparing about 3-4 line answers to most of the questions that could come up in the exam. I wouldn't prepare heaps and heaps for each question as the examiner is bound to cut you off and ask you other questions as it has to be really conversation-like. When you're writing answers try to think of what the examiner could ask you that would flow on from the previous question, and prepare for that as well.
Also, i think it's so helpful to research what you're talking about, and to be able to form a strong opinion on the topics, or an area of the topics that interest you, because your apparent interest in the topic and opinion will show and make you stand out. So you could prepare to talk about something that you saw on the news or researched, or something to with for example, the teenage consumption of alcohol in Germany. It's not actually required to link what you are saying to Germany, but it will just set you apart abit
As well as preparing short answers to most questions, i find it really helpful to make a vocab list of words that you could use in every topic, things like "i agree with you" and "thats a very contreversial topic" etc. to help the conversation better.
And also, use your textbooks and kerboodle! If you read through the texts there are soo many useful phrases and phrases you can use (and you already know they are gramatically correct haha) and so much vocab that is specific to each topic. And learn loads and loads of vocab as well, it will help to say things more concisely and will make you be able to say things more spontaneously
I've made a prep schedule of when i want to finish each topic, i don't always stick to it but it helps me keep more or less on track!
Really hope this helped and makes sense and good luck!
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