It took me 2 weeks. Before that I made 10 guys in the same position
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.
Okay, what kind of game are you making? It is a platformer, right? And I guess you use the built-in platform movement for your character? And also, when your character shoots, you make him shoot by using the event action "Shoot an object", right?
If all these are true, then you must know that your character object are constantly changing direction while moving around, and the "Shoot an object" event action shoots an object at the same direction that the object is facing.
One simple way to do this is that you can use a value again, namely your main characters Alterable Value A (you can always rename the value to "Shoot direction" to make it easier for yourself), but you don't have to set the default value to anything. Now, just make so when you press Left, set the value to 0, and when you press Right, set the value to 1.
Now make it so when you press the shoot button and the value is 0, make him/her shoot left, and when you press the shoot button and the value is 1, make him/her shoot right.