only grow one bunch, then that particular stalk/trunk whatever, will die. There should be suckers forming at the base of the plant
. Allow one of these to grow and it will be your next seasons' crop. The idea is to have one producing, one half grown and one little sucker just forming at the base of the stool.
Once the fruit have set, you can cut off the purple flower
bit from the end of the bunch. It is just taking nutrient and generally doesn't continue setting fruit. So snip it off.
You should cut the whole bunch down when the fruit have fattened fully and maybe just starting to colour. Then you can hang in the shed, (not you, the bananas,) and 'hand' them off as they ripen with a sharp knife..
As i said, that 'trunk' will then be finished. Some people cut it off at ground level but i prefer to cut it off at about 6' high and let the water in it slowly drip into the rest of the developing stool.