1. Above all, please don't write out an essay in English and then try to translate it into German. This will be an awful amount of work for you, and using a dictionary to try to do a lot of things you haven't learned just leads to lots of misunderstandings. Doing this often causes students who have worked very hard to get bad or mediocre grades, because the result is often incomprehensible.
2. What's easier
and much more fun is to try to put the essay together using the German you have
learned: write down relevant nouns and verbs first. Look up only what
you know you'll really need and want to use. Look up words you've found in the
German-English part to check that they mean what you think they do. If you use an online dictionary, we recommend PONS; try dict.cc or possibly LEO if the PONS site is slow or you want a second opinion.
--then make very simple subject-verb-object sentences out of these verbs and nouns.
--now see if you can add anything else you've learned: connect some of your sentences using und, denn, sondern, aber, oder. Add some adjectives and words like "manchmal" or "oft" or "leider."
--vary the word order in your sentences, i.e. put something other than the subject in the first position of a few of your sentences. Remember the conjugated verb always comes second, and the subject comes right after the verb if it is not first.
3. Writing in this way will make you write better: the linguistic limitations can inspire you with fun ideas, and writing clearly and simply is the best way to write in any language.
In general, the more you can put your essay together in German, the better!
Other specific advice:
1a. If you use a modal verb (können, dürfen, sollen, wollen, müssen), be sure to conjugate it correctly - click here to see their present tense forms. Remember in particular that they have no endings for the ich- and er/sie/es-forms. Remember also that the modal verb goes in "position 2," and the infinitive form of the "other" verb comes at the end of the clause: "Nena kann gut singen"; "Heidi Klum will das nächste Top-Model finden."
1b. The same rules about verb position apply for möchte: put the infinitive form of the "other" verb comes at the end of the clause: "Sebastian Vettel möchte einen Ferrari kaufen"; "Ich möchte Fatih Akin kennen lernen."
1c. The above list of modal verbs should have included mögen, but it didn't because mögen is normally used with nouns rather than other verbs: "Angela Merkel mag Nicki Minaj, Bruce Springsteen und Peter Fox"; "Jerome Boatengr mag Katzen. Er mag keine Pressekonferenzen." But mögen does follow the same conjugation pattern as the other modal verbs: no endings for the ich- and er/sie/es-forms.
2. Proofread your essay: look up the genders of all nouns; for any nouns in the plural, look up the correct plural form. Use a German spellchecker. Many Word Processors now automatically detect the language of your text and spell-check accordingly. Otherwise, just highlight the text, set the language to German, and spellcheck as you normally would. If you can't get this to work, ask a friend, or a computer help person.