Don't worry, your English is okay!
What I did:
1. Decrypted install.dns
2. Unpacked the decrypted dns (either with utf tab special or the x-cpk bms script)
3. Modified one line using hkki.
4. Tried to pack it back with cri file maker, but it didn't work properly: my original file was about 125 MB, but the outcome file was 250 MB.
5. As expected, the game crashed as soon as I reached the dialogue screen.
I don't have access to my computer now, but I'll check that cri maker you mentioned soon. Thank you for the tip!