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Let's talk over a cold beer.
Literal
Chilled beer [or-でも] drink-while talk-[let's-ましょう].
でも ('or something like') softens a suggestion — 'a beer or something.' ~ながら ('while') attaches to the い-stem to mark simultaneous action. 話しましょう is the volitional polite ending ('let's talk'). Natural and warm invitation.