If you want to have persistence over several scenes, you need to use global variables. Before going to the previous scene you can save the number of instances of your enemy in a global variable with the SceneInstancesCount()- expression. And then you use this variable for creating the correct number of enemy instances when you come back to the scene.
Btw you have a ‘repeat for each’-event together with a “trigger once while true”- condition. This is not working as you expect "Trigger once" with "Repeat for each instance": different result than expected. For creating the energy/health-bar you can put the loop in a subevent of an “At the beginning of the scene”-condition to make sure that the objects are only created once.