All you can do really (aside from learning prepositions/tables off by heart) is expose yourself to the language as much as possible. Read Zeit Online/Der Spiegel every day, watch movies and do the Video Thema stuff on Deutsche Welle. How bad are your mistakes though? As long as you remember the 5 words above that take normal word order, the "time, manner, place" and "verb 2nd idea" rules, you should be OK as far as word order goes.
As for essay writing (which I'm not great at myself), make notes for all the relevant topics, including advantages/disadvantages of stuff (e.g integration, nuclear power, tourism, sport, etc), and at A2, quotes (your marks will shoot right up if you include relevant quotes from Angela Merkel and other important people), key dates and events, and things the government are (not) doing to fix things in Germany. It's a good idea to collect some synonyms too so you're not just repeating "Kernkraftwerk" or whatever over and over again in your essay.