Apart from structure, one or two sentences as introduction and conclusion. The remaining of your word limit should focus on the body. Content should be descriptive, storytelling style - how did you travelled there; whom with you travelled; where have you stayed; what have you visited; what did you liked about this holiday. Answering these questions should be enough for about 150 words. You can make your essay better with using higher level vocabulary (Sehenswürdigkeiten, Rundreise, Unterkunft, Andenken etc.) We'll revise these words later on.