Hello, dziadzu, and welcome to the forum. I am sorry that your dad has been diagnosed with liver disease. If you read some of the older posts, as well as the educational posts on pages 1 and 2, you will get a better idea of some of the things your dad will face. There is medication to stimulate appetite and you might ask about that. Also, meal supplements such as Ensure are often used.
The encephalopathy is caused by high ammonia levels. Usually Lactulose is given, which works through bowel movements to remove the excess ammonia from the system.
I hope that your dad will start feeling better soon. You will receive a lot of information and support here, so please continue to post.