Consult the following German-English/English-German dictionaries for sentence examples, sample letters, useful phrases for essays, and other types of writing.
Collins German Dictionary
REF PF3640 .C64 1999 (Reference) - See the Language in Use/ Sprache Aktiv section (shaded mid-section of the book), especially "Essay Writing," for excellent examples of how to explain, develop an argument, express opinions, and much more.
Collins/PONS Deutsch-Englisch English-German
REF PF3640 .H28 1997 (Reference) - Same content found in the preceding dictionary but in a different lay-out.
Oxford-Duden German Dictionary
REF PF3640 .O94 1999 (Reference) - See pages 867-899 (shaded mid-section of the book) for examples of letters and useful phrases.