Making small talk is difficult because you never know where the conversation will go!
Chatting is hard because you never know what topic will come up next!
make small talk = スモールトークをする
you never know = 予測がつかない・いつもわからない
例えば “He doesn’t say much so you never know what he’s thinking.” (彼はあまり喋りませんから、何を考えているかいつもわかりません。)
topic come up = 話題が出る
例えば “She was sad when the topic of travel came up because she didn’t have the money to go anywhere.” (旅行の話題が出た時に彼女が悲しくなりました。どこかに行くお金はなかったからです。)