How do I add some spikes that will harm the player?

Hello all, is there a way to add an obstacle (such as spikes) that will harm the player? Also, how can I make the enemies follow the player? I have tried to add a bullet behavior and have made some changes to my event sheet but my enemies start moving to the right and when they see the player they start following him whilst rotating.

You need to read some tutorials:

https://www.scirra.com/tutorials/all

Add a spike sprite, on collision with the player subtract from player's health.

Your enemies are rotating because you have "Set angle=yes" in Bullet properties.