How to make a obstacle that would reduce timer if stepped on

I’m trying to make a obstacle that would reduce timer if stepped on, I don’t have much experience with blueprints.
I’m going to try and show as much info a possible and an explanation would be great!
Here’s my timers functionality to get it to start counting down when I start the level


Then here is what makes it display on my hud

Then here is a bad attempt at making the obstacle which did not work