Practice below english conversation so you can automatically speak them out when you want to warn foreigners in urgent situations.
Example 1
You : Watch out for the car!
Friend : Thanks. That was close.
You : It's ok.
Example 2
You : Look out!
Friend : Thanks so much. It could hurt me.
Example 3
You : I think you should be careful when you talk about your boss like that in public. You could be fired.
Friend : Well, thanks for the warning but I don't really care anymore.