1. Elena y yo/preocupado -> Elena y yo estamos preocupados [plural, masculine form of the adjective]
2. Juilian/nervioso -> Julián está nervioso [singular, masculine form of the adjective; the Spanish correct form for the proper name is Julián]
3. Ustedes/hotel -> Ustedes están en el hotel ["hotel" is not an adjective, but a noun; we must add a preposition and a determiner for the sentence to have sense]