@Andrea522,
I'm getting people from all over and there are always guests, who think the star system means 5= excellence, 3=normal and 1=avoid. I can't really blame them for it, I thought that too. Only since I'm an airbnb host and adapted to the system, I rate products by maximum stars = ok, one star less than maximum = average and the rest is to avoid.
People from some nations will generally see it that way, but you should get a few 5 stars from time to time even then.
Your stars show 4 on precision and cleanliness, the other categories are higher rated. So you should work on those two categories. Some reviews speak of bad smells and an open trash can in the kitchen. Maybe you try for a while to empty the trash at least once a day, especially after cooking or throwing away smelly packagings. That's not such a big effort and will improve the feeling in the kitchen. At least close the bags and put them on the balcony in the evening to take them down in the morning. It looks like your apartment is clean, probably as clean as 5 star ones in most aspects, but you get dumped because of small things, like the trash. You could get the living room more inviting by putting some curtains, a picture on the wall, which would hide the holes left by some former furntiure or wallmounted tv and a few tourist brochures in the white shelf. Small stuff like hairs in the shower drain or stains on the mirror reduce the stars too.
For the precision rating, you should work a bit on your description. You call it a B&B in the title. For me, one of these Bs means breakfast, but it seems not all your guests get it or you do not offer it. Then you speak about your flat with all the rooms. So, is that a full flat? As a host myself, I know how to look to finally see the Private Room, but I bet a few of your guests did not really know what they booked. It was nice after all, so they leave a good review, they know in hindsight, that they should have seen it, but there is a little anger left, so they give you less stars on precision. That rating does not mean: Is the host precise? It means: Did you understand?
People come from different countries and backgrounds, there is a lot room for misunderstanding. Rewrite your listing, as if you wanted to explain it to a child of a friend. A child, because you have to lower your expectations, what the guest will take for given. Guests are so different, there is no common base. And imagine yourself explaining it in person, when you rewrite it. Your reviews say, that you are a sociable very nice person, so you are a warm human being and generous when you meet people, you are better at telling a story than writing one.
At the moment, you have a list of things, try to make it a warm and useful description. Describe the apartment, but relate it to persons, yourself and the guests. People want to orient themselves, so what is that place: an apartment, where you live, alone or with others, is it new or your home since you were born (exemple), your main apartment or a second apartment or a place where several rooms are rented to strangers?
Then describe what the guest can do. A room to spend a quiet night / a room with a comfortable bed to relax, a bathroom shared with the host, more people or for the guest alone, a kitchen to enjoy breakfast - provided the trashcan was emptied 😉 - or to cook dinner as well, a living room to watch tv or chat with the host whenever they want / withhin certain hours, / or you may invite them to the living room.
You say close to the bus and train stop: indicate the lines and name of the shop, maybe the time it takes to a few attractions of Lausanne. Indicate what kind of shops and restaurants there are. At your price level, people will be interested in cheap restaurants or buying groceries or take outs. Add a few pictures of the area, a favourite restaurant or shops. Everything that helps people to feel they know the place when they arrive.
I took photos from the metro stop to close to the entrance of our alley, all around the place where they arrive. That helps a lot that they can orient themselves when they arrive, it shows the possibilities for shopping and hanging out and it brought both precision and location ratings up.
Just imagine: you go to a strange place, to live with a strange person and everything looks surprisingly different from home. How scary that is! If you can imagine beforehand how it will be and then you find everything easily, that's a much better start for a holiday. No difference to the place, only more information.
Good luck!