Dog problem please help i need a lot of it because im scared lol?

hi i have a dog called Chuda its Russian for crazy and it bothers me because somebody left a dog at our gate and they abused her we decided to keep the girl and named her Lexi. The question i have is my original dog which i love a lot a lot i mean and he is not eating. well i know he eats a little but he is starting to show his ribs and all he does is bark all day we are getting Lexi fixed but its still scaring me because either way i don't want to lose Chuda. I need help and does any body have a suggestion we are not taking him to the vet because she is going to tell us hes going to be okay just feed him and we already are so i need help please don't comment anything like take him to the vet or i have no clue or just separate them or shes in heat thats why, i already know these things i need help on how to make him eat his food. So thank you and please help. Oh and i know i have a lot of run-on sentences but still im just worried thats all thank you to all.