I don't know how feasible this is because I don't know how attributes of polish AC7 and English AC9 are different, but is worth a try.
Create a new Project in ArchiCAD 9, and merge the polish AC7 file into it.
ArchiCAD refers to attributes by their index number, not by their name, so it might work, although I think you will still have a lot of adjusting left after doing this.
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