"You are going to have a lion?"
Translation:Tu vas avoir un lion ?
The construction for near future is relatively similar in English and in French;
- conjugated BE GOING TO + INFINITIVE verb = you are going to have
- conjugated ALLER + INFINITIVE verb = vous allez avoir
"Aurastu un lion" is also right although they don't accept it. I think it's more grammatically correct seeing as it's a question and the inversion subject/verb is required. In spoken language though it's largely accepted to ask "Tu auras un lion?".