My special respect for your father increased ,a person who sacrificed his life for Islam and Iran.
I think your question about how we can trust others is not easy . Upon a fact that some people didn't show their true color ,we can't trust anyone , we also should respect others and should be unsuspecting to others in first step.
How we can trust on others? Respect, responsibility, fairness,honesty, caring, loyalty and commitment are common criteria for every body to be trusted ,but it is not enough ,We can't trust to a naïve and credulous people ,because they speak everywhere and reveal something that were supposed to be secret between you.
I had a friend when I was in high school , He showed me what I think about a good person. He was also a good student, artist , painter,his handwriting was wonderful ,he spoke French well, but I didn't trust him because I discovered some slyness in his behaviour. He tried to change my belief, he tried to change my look toward some principals, on his last effort he tried to set up a relation between his sister and me. Finally when he was disappointed he told me that I was the most pertinacious person he had seen. I never follow him and never trust him.
Lucky, you are young and clever and you know how to trust people, especially how to trust people via internet.
All the best