I have a dog, and even tho they're at my grandparent's house so we don't get to meet often, but I really cherish the feeling of having a pet, and I'd most likely feel torn if my dog got sick, so even tho I can give condolences, I'd rather ask you to spend as much time with it as possible so that even if it passes away, you both only have happy memories.
I'm heartbroken to hear that my Dog passed away 3 months ago from lime disease so I understand how hard of a time you're going through I'll be praying for you and your dog
Spend quality time with the dog be present. And stay away from sad dog stories and movies (Old yeller, sounder, Mumu).