How do dry bays protect against fire, and do civil aircraft also have dry bays like military aircraft?
Yes, civil also aircraft have “Dry Bays” but they do not protect against fire. A dry bay is an area adjacent to a fuel tank that holds various components.
Some aircraft (mostly military?) have fire extinguishers or fire suppression equipment in dry bays but this will vary considerably with each type. (the B777 has no fire suppression in the dry bays)