If people want to do something dangerous you could warn them ,saying I wouldn't do it if...

If people want to do something dangerous you could warn them ,saying I wouldn't do it if I were you . What would you say to these people .
1. Someone's car has no brakes .
2.Someone's going to swim ,but the water is wery cold .
3. Someone's going to drink the milk .It's not fresh.
4. Someone's going to eat the cake. It's two weeks old .
5. Someone's parking his car in a no -parking zone .
6. Someone's going to buy a car from Denis Cook This person has a very bad reputation .
7. Someone's going to buy a washing machine from Mrs James.
It doesn't work properly .
8. Someone's going to an African country to spend his holidays there . The political situation in that country is rather dangerous