In these examples, down and back are not prepositions but function as adverbs to extend or change the meaning of the verb. This combination of verb and adverb is always known as a phrasal verb.

Phrasal verbs are verbs with more than one word like 'wake up' and 'look forward to'. There are hundreds of them in English and they can be quite tricky... But don't freak out! Georgie is going to ...