This is a common issue where multiple animations are trying to play at once. You have to use conditions that make sense to ensure that none are played at the same time. For example here you are trying to play 'attack' and 'walk' at the same time, so you have to add a condition on the 'walk' event such as 'attack animation is not playing', this allows attack to play and then return to walk once finished instead of trying to play walk anim at the same time.
edit : I misread the animation it's 'hit' when an enemy gets hit by something but the same logic applies, you add to the walk animation event a condition like 'hit is not playing'. Also the ogre should die because receiving damage should be separate from the animations, such as 'bullet on collision with ogre then take damage' rather than on hit animation played.
For falling through the floors and strange bugs around that, take a look at the collision box of the ogre in the image editor, make sure it's a box and not a random shape based on the image.