I started a journey with a person I had recently come to know…

I will take up your dream and endeavor to provide an interpretation without asking you any questions, for SOMETIMES it is possible to interpret pretty well without any information about the dreamer's real situation, and you have given some information as well as some more specific details of your dream. The problem that you're creating that could get in the way of an expert interpretation is that you are assuming that the dream is not symbolic for how God is showing you to move forward on your spiritual development, but more specifically it's narrowly about what to expect from may be a planned marriage to a man you have nowhere near enough personal experience with to judge intelligently&intuitively whether to entrust your future to him or not.
After carefully reading both your dream and your extra information about it, I am inclined to BELIEVE your attitude that sometimes God DOES give you rather blatant symbolic AND real imagery for gaining the meaning of your dream. So I will interpret the few symbolic elements in your dream in relation to what I can understand about the real situation you're dreaming about.
First, your sister's report about the quality of the man's deceased wife does not prove that he will treat you in ways you are comfortable with once you are in his territory--because his expectations from marriage are already well formed, and they may not fit well with your expectations. And that's the concern your sister brings up second.
Second, the fact that you are Walking, and it's a very long and hard walk suggests that this marriage will be a big change from what you're used to and will challenge your abilities and endurance--and in fact many women in middle age will say it's much more difficult to be married than to be single, because taking care of a man's needs and pleasing him also can be burdensome and can outweigh the rewards you may be expecting to get.
Third, the wetness apparently coming up from the green grass onto the man's pants almost to his knees, feels to me like it's somewhat damaging to your shoes and clothing, since it's getting his shoes and trousers wet. "Getting your feet wet" is a metaphor for trying out something new (which the new green grass is also symbolizing) and the water involved symbolizes emotions you can't know in advance, and they're compromising your clothing--so you're not happy about what you're feeling and how that's affecting the outward personality you are used to expecting yourself to manifest, that is how these new-relationship feelings are "getting your self-image wet."
Fourth: Most important here, is that the man you expected to be getting to know is suddenly not walking WITH you, but ahead of you, where there's no chance of getting better acquainted. And he's become a STRANGER who expects you to walk behind him--like a dutiful wife should. This is the OPPOSITE of what you might expect to happen: You don't get to know him more intimately "on the way to the wedding," but you get put into the role of follower and subordinate before you even get to his village or home. And at this point, you realize that in fact this man is a stranger, because you don't know him yet. And it's quite common in many cultures that a man presents himself as kind, generous, understanding etc. when he's trying to get you to marry him; but once you agree to be his wife, he may become a different person and show you a very different personality entirely. This is the turning point of the dream.
Fifth, as you leave the ground, where you're walking in contact with solid earth, to climb the stairs after him, your fear of falling is a strong symbol of knowing you are not connected to the roots of your life as you've lived it for many years, and there are not enough protections to keep you safe. This image may relate to the actual building the widower co-owns, but it's also a universal symbol for going upwards, by your own efforts (step-by-step) to reach a new and ambitious height. But your own personality realizes that you've never been here before, and mistakes any could hurt you very badly.
You feel out of place, and you are losing the person that you came to the building as, because there's a number next to your name. This is further symbolism that you don't really matter as a unique person to the widower, but you might even be a prisoner. It appears that you might lose your identity if you marry this man you don't really know, for he is literally a stranger to you and you are a stranger, with a number, to him.
You came to view this unprepared marriage as an evil project, and you call upon God to protect you--which he comes to you from your unconscious to do. Because you believe that God will protect you from evil, and you become afraid of this marriage to a widower who you don't even know, your unconscious shows you that you are too far outside of your comfort zone in trusting your life to a strange man just because he wants to marry you, so your dream justifies backing out of your (was it negotiated over the Internet?) arranged marriage commitment.
You could decide that the dream just shows your fear of a risky marriage commitment and the man isn't really evil and just insist that you need to spend several months getting to know him before you decide whether to marry him or not. For the dream definitely shows you that you are way to scared of such a blind commitment to marry a man you don't know to go through with it the way it's presently planned. Or you could take the dream as the true story of what would happen in the future if you tried to go through with the proposal--and in that case you'd just say NO to the proposal so you won't have to "get your feet all wet" and reach the point of panic and calling on God to save you.
It's actually NORMAL to be afraid of getting married, because it IS a big and long commitment and it DOES change you quite a bit, into a new person (stranger) and it can even imprison you in a situation you may not like (the number next to your name).
The dream is definitely God's wisdom in that it's showing you that it's too scary (therefore dangerous to your future) to agree to marry a man you don't know. So do take the hint from God and make sure you spend at least several months getting to know any man you might consider marrying.