The fact that it's dual language might make this a bit annoying to work with, but I've run some tests and Translator++'s V2 parser seems like your best option for simple dialogue.
You've probably already done that, but you make your life a lot easier if you decrypt the game first.
Extraction Tutorial
Using
Translator++ Ver4.7.30 standard edition 64bit, you just run it and tell it to download the Ace package. (Ignore the "missed updates" message, this is a cracked version, updates do not work)
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You then start a new project using the V2 parser and select the executable of the game.
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This step will take a long time because that game has a huge amount of text. Unless you have some high end monster rig it will seemingly get stuck several times, but just give it 30 minutes, it will eventually finish parsing.
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Now definitely save the project as a ".trans" so if something goes wrong you don't have to go through the initial parsing process again.
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Next go through the different parsed files and put your changes into the cell to the right. It will only ever process the most right cell.
(If something is in "Initial", in "Machine Translation", and in "Better Translation", only the "Better Translation" cell will be used.)
Please keep in mind that you need to take care of word wrapping and formatting. If you make your sentence really long and you don't break it up in multiple lines your text will escape the screen and not actually be fully visible ingame.
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Once you finished your changes you export the project. This will once again take a very long time and seem to be stuck, but it's not, just give it time. Should it actually permanently freeze for more than 1h, then you can also just select which files you want to export at once and make smaller packages.
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And for just changing some basic dialogue without fancy text effects, scripts, popups, or whatever, that's it.
You now have a patch you can extract into the game and permanently apply your changes. (I recommend not actually using the version you parsed with Translator++, and testing on a backup instead.)
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Edit: I obviously don't know if it really successfully got all of the dialogue, but even if it didn't you can then just parse your already modified stuff with a different tool. The only issue might be the dual language stuff because that is not a standard Ace thing. So we don't really know how the game handles choosing the correct dialogue box.