Walking across bridge help

I am trying to make that if you interact with a tree you get 4 logs. I have 3 trees in the map and each one gives you 4 logs. There is a river that splits the map in half. I am trying to make it that when you interact with the river and you have 6 logs it will build a bridge. I got that working although I do not know why but you are able to walk across the one part of the river when you still have not got any logs or anything. Can someone please help?

Can you show us a screenshot of your map and the eventing? That'll help us to figure out what exatly your problem is and how to fix / improve it.