1. So are you requesting GDL manual in local language? FYI Someone from GRAPHISOFT KOREA kindly translated the English manual into Korean. you might be lucky to have a copy if you contact Doallteck,
2. there is a sublime addon that supports GDL syntax/highlighting feature.
3. I also recommend reading GDL cookbook. it may be an old manual but I haven't seen anything better than this.
4. Built-it GDL syntax/highlighting feature/pre-coding/searchable would be great. who knows, it might come to us in the near future.
5. last but not least, no matter how good the reference book or AI is, I recommend digging into other's GDL scripts. you learn both good and bad techniques.