@Inbal11 Your listing description is pretty brief- I would give more information there. You should make it clear to guests whether there are common spaces that they are welcome to share, like the living room and kitchen. I see you only have photos of the bedroom and bathroom, so that's good, that you aren't showing the rest of the house that you don't want guests to use, but some guests may make assumptions, so you need to make things unmistakably clear, both in your listing description, in a message to guest when they book or request to book, and when they arrive.
If you don't mind guests using the living room, but are just upset that this particular guest is making himself way too much at home there, then really all you can do is be straightforward with him about him taking over your living room and sleeping there- common spaces are not places to sleep unless they are set up that way. If he's only staying for a few days, I'd let it go. If he's staying for awhile, you need to set some boundaries. To be fair, older people often don't sleep for long periods at night, and sometimes easily fall asleep for short periods during the day without intending to.
As far as a review goes, I wouldn't mention him using the living room, as you haven't made that clear, it seems, just write an honest review. If his hygiene is bad, give low stars for cleanliness, but don't mention his age or his forgetfuness- that's too personal for a public review. If his forgetfulness caused him to forget to do things you asked of him, like turning out lights when he goes out, or not hanging wet towels over the furniture, then jus say that he seemed to have a hard time remembering to follow simple instructions and house procedures.
