put so many bad things on this earth? like cancer, drugs, evil people?

Read the Bible, the fall of man.

man has their own will of thinking, so they can choose to or not to obey God's commandments, in which many fall to temptation, thats one reason.

Wrong, we ALL fall into that temptation.

pardon me, but i think you should know where I am getting at lo, anyway yes, we all fall into that temptation..

try to sound more polite, you sound stern to me.

You can't change my personality in a single sentence. You can't tell a cat to suddenly not chase lizards and grasshoppers.

There is a very good reason why I act so hostile and that looks as though it is here to stay.

Just one of the consequences of the fall.

it won't be like that in heaven

Yep, its man that corrupted this place.

There was no war, cancer, etc.. when the Lord made it.

its only part of life..

He allowed people to grow, therefore, allowed people to make mistakes, which in turn, led to all that.

Everything has a positive/negative.

Drugs, most of them started off with good purposes, that are meant to heal, to help, but our never ending search for more knowledge, we turn it, as well as everything else, we find it's other side.