Welcome to Hive
If I were you, I would really start out with something smaller. An ORPG is a rather massive project and usually they never get finished due to the enormous amount of time required, adding to that you have little experience, so it just becomes more complicated.
Still it could be a very good learning experience to attempt, but try to make something smaller as the main thing. Perhaps find out what mechanics you could imagine for your ORPG, plan it out and then make smaller maps each dedicated to their own "part of the ORPG". Then you get experience working with the different elements required, you might learn something new doing it and find inspiration for the final piece; the ORPG.
I myself have begun and then never finished a campaign, due to the massive size of even simple things. It is many years ago, and I would likely find it a lot easier to do and actually finish now (not including my busy RL schedule). So ambition is a good thing, but take the time to look at the included tutorials and try things out.
You could already now make a project thread for it.. where you can post ideas, inspiration and everything. Basically showing a plan and what you want to do it with it.
At any rate it is good to have new people here, and hope some of what I wrote might help you onward with your modding journey.
Once again:
Welcome to HiveWorkshop 
) I would like to ask for some help. (If my english is wrong sorry because I'm Brazilian 
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