I don't want my girlfriend to go out to dinner with a male friend from college
Are you serious? Why don't you want your girlfriend to have dinner with a male friend from college?
I do not trust his intentions
You are behaving in a controlling way and you need to loosen your grip on your girlfriend. It is not your decision who your girlfriend goes to dinner with. If you continue to be so controlling, she will consider breaking up with you.
It's my decision since she's my girlfriend. If I can't trust my girlfriend, I should break up with her.
If you are that untrusting of her, then perhaps you shouldn't be in a relationship. You shouldn't be so worried about who your partner goes to dinner with if you're in a loving relationship.