Well, that's another topic... I recommend you to start, and to know some basic aspects of renpy, watch some youtube tutorial.
Learn how to define variables and how to modify them (character stats).
Learn the basics about "screens".
For example:
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Then you can also check the official documentation where there are also some examples, although I must admit that it's not the first place where I would send you, better to see some basic practical tutorials first.
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