Train station - symbolizes moving toward new opportunities, possibilities, and changing scenes, ie: from the family environment to the work environment, from an old way of life to a new one, leaving behind old hurts, bad memories, or relationships.
Train - If you don't normally take the train to work and it is a part of your daily experience, the train could be symbolic of your need to move on and to do things in an orderly and sequential manner. Also, may represent conformity and going along with what everyone else is doing.

Young girl -  For a female to see a girl, and if she reminds you of someone you know, it's a representation of an aspect of that person you recognize about yourself, or would like to.
If you do not recognize her, or she does not remind you of anyone you know, she would then represent your playful, innocent, and childlike nature. Perhaps you have been behaving 'girlish', or immaturely, about something or situation. It could also be your maternal side taking over.
For a man to see an unknown girl, signifies that he is becoming aware of, or recognizing and acknowledging, his younger, feminine, side.

Uniform - This could be hinting at something in your life which you feel you have some sort of duty or obligation to. It could be a symbol of conformity or thoughts shared by others as well.

Jumped off the platform - Suggests you're feeling the need to get out of something in your waking life.

Someone else committing suicide - if you know the person, it highlights your concerns for that person. Otherwise, consider what characteristics and qualities in that person you may be trying to "kill" and annihilate in your own self. Perhaps you hope that you are not like that person in some way and are making attempts to get rid of those traits within your own self.
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Are you feeling as though you are just going along with everyone else, that you don't feel or express your own individuality?
Is there a desire to change your lifestyle, or a current relationship?
Are you seeing a different side to your personality that you don't particularly like?
Is there something, or some part, of yourself you are trying to get rid of, or 'kill off'?
Is there something you're trying to get out of....a relationship, responsibility, appointment...etc., or something you are hiding, or don't want to face?
Did someone accuse you of acting childish, being silly, or acting like a little girl?

Hope this gives you something to go on, best wishes!