Instead of telling me one thing at a time, it would be better to tell me everything at once.
I would prefer that you tell me everything at the same time rather than little by little.
ーInstead of telling me one thing at a time, it would be better to tell me everything at once.
「一つずつ言う代わりに、全部一度に言ってくれる方がいいんですが。」
tell one thing at a time で「一回で一つの事を言う」
tell everything at once で「全てを一度で言う」
ーI would prefer that you tell me everything at the same time rather than little by little.
「少しずつより、同時に全部言ってくれた方が良いな。」
tell everything at the same time「同時に全て言う」
rather than little by little 「少しずつ・小出しより」
ご参考まで！
カナダ 
