Banana trees/plants grow differently from trees, as they are large herbaceous plants (genus Musa) . The upright part that seems like a trunk consists of the bases of their leaf stalks/petioles, which are tightly curled together circumferally. This pseudostem grows from an underground rhizome (the visible part of the base above ground is called the corm). Each banana pseudostem produces 1, or sometimes more than 1 cluster of bananas, and new pseudostems/ 'new banana plants' that grow up from the rhizome of the plant can each produce 1 or more clusters of bananas!
After harvesting the cluster of bananas, maybe check if there is 1 or more new pseudostems/ 'new banana plants' growing up from the underground rhizome. And maybe wait before trimming off the present pseudostem until it's clearly observed to be withering, because it could be forming an additional cluster of bananas! If the pseudostem has ceased to produce, it will wither as the plant withdraws energy from it! Then, after the spent pseudostem has clearly withered, then carefully trim away the withered pseudostem, being careful to preserve new pseudostems capable of producing bananas that may be growing up from the rhizome!
Allowing the harvested pseudostem to remain until an additional pseudostem (or pseudostems) can grow up from the rhizome enough to be successful & until it's clearly withered can benefit your banana plant, since the leaves of the harvested pseudostem may still be contributing some energy to the rhizome! The underground rhizome needs to remain in order to produce new pseudostems, each new pseudostem/ 'new banana plant' capable of producing 1 or more clusters of bananas! New pseudostems/ 'new banana plants' bear new clusters of bananas in about the same amount of time as the original banana plant.