Hi,
it's hard to tell without knowing your capx
but I try it anyway:
lets say you want to subtract 1 life on touch then it is important not just say "on touch" (here it would affect all enemies). You have to take "on touched object"
with the walk left/right I have no idea what went wrong - so here a solution that works
in this example you have to give the enemy a bullet behaviour, an instance variable "WalkingLeft" to false (if they start to the right), and an object they can collide with
obj_Enemy > on collision with obj_Wall
subevent: obj_enemy | is WalkingLeft || obj_enemy | bullet speed = -100; obj_enemy || set WalkingLeft to true
subevent: obj_enemy | is NOT WalkingLeft || obj_enemy | bullet speed = 100; obj_enemy || set WalkingLeft to false
hope this helps