So sorry to hear about your boy, so young too.
I lost my last boy 5 years ago to DCM/CHF. He was 7. When he was diagnosed the Vet put him on 4 different types of medication, Vetmedin(Pimobendan)Fortekor, Spironolactone & Frusemide. When it came to food/feeding he would eat his regular kibble just fine until the end was near. Then it became a job to stimulate his appetite. So I would tempt him with anything I could think of, chicken, beef etc, gravy, soups. I've seen people recommend wet cat food, strong smelling fish, hambugers, hotdogs, sugar covered cereals. Anything really, just to get them eating.
As the disease progressed my boy couldn't lay on his side due to the fluid build up. He would lay in what they call the Sphynx position. The dreaded coughing became more frequent, his gums were very pale & his ears & feet would feel cold to the touch. We let him go 4 months after diagnosis. We had reached the limit on his Frusemide & it was no longer effective. He spent his final night unable to settle at all with my husband by his side the whole night. He was euthanised first thing that morning in my sons arms with me by his side.
I'm so glad to see your boy has stabilized. Hopefully, whatever medication he gets will soon kick in & he will be able to go home with you.
Sending positive vibes to you & Leo, please keep us updated.
Oh, & you're doing just fine with your English. No worries there.