「はい」と「いいえ」しか言わない人と会話を続けるのは難しい。

「」「」。

It's hard to keep a conversation going with someone who only says "yes" and "no."

Literal

"Yes" [and-と] "no" [only-しか] say-not person [with-と] conversation [object-を] continue [nominalizer-のは] difficult.

A long nominalized clause. The relative clause 「はい」と「いいえ」しか言わない ('only says "yes" and "no"') modifies 人 ('person'). The whole resulting phrase 会話を続けるの ('continuing the conversation') is nominalized with の and marked as topic with は. しか~ない restricts the person's utterances. Note the two uses of と: conjunctive (joining はい and いいえ) and comitative ('with').