Hi again Little Stain! Thanks for replying me again!
Your reply have a perfect logic, so I tried to apply it! The first part I did in the way you said, but the second one I can't understand how to make that happen in C2, in the Variables events there are nothing such as "check boolean"... am I wrong?
This is very basic stuff, that you should know if you've read the manual and done a few tutorials.
Have you given your player a Boolean variable?
If so, then adding the condition LittleStain suggests should be as simple as:
Click on Add Condition, Select Player, select 'Is Instance variable Set', and select the GotKey Boolean. Add the Door collision check as another condition, and you should then be OK to set whatever Actions you need.
If your vision so exceeds your ability, then look to something closer.