The in French is OK for me.
Open wpr-giftcards.pot with a software for the translation (ex:Poedit)
Customize the content.
Save the .po like that (rpgiftcards-fr_FR.po) Change Fr_Fr for German maybe ge_GE i dont know.
Now you have rpgiftcards-ge_GE.po and rpgiftcards-ge_GE.mo.
Put them in the folder wp-conntent>langauges>plugins.
For me it works.
Good luck ??