@Mel101, I'm also an in-home host in a European capital, so the variety of guests you get over time will be very similar to what I've had over the years. The one you have in this case seems to fit a particular category: the city-hopping Euro traveler. Most of the time these are easy and decent people to host, but there are a few details that make them different from the single-destination City Break tourists:
1. They have made several different accommodation bookings for the many legs of their journey, and are therefore easily confused or forgetful about the details of each.
2. Their sole internet access tends to be via their smartphones, and their foreign mobile plans often don't cover the EU affordably; therefore, they might only be reachable when they have free WiFi and a charged battery.
3. Since they're visiting several places, they're unlikely to have done much research about any particular one, so they'll arrive with less of an idea what they're doing in your city.
4. Traveling overland, their arrival times are subject to any number of changes and delays.
5. Their journey is often already in progress when you contact them, making their response time more erratic, and they may already be experiencing stress or fatigue from the trip.
These are all things you can easily manage as a host, provided that you set a few parameters to lessen the impact of erratic communication. Firstly, make a check-in window default on your listing. Next, just as you ask for 2 days notice when requesting dinner, also ask for minimum 2 days notice about approximate arrival time. You can still state in your rules, as I do, that it's sometimes possible to make exceptions if guests request them before their booking is confirmed. But once a booking is confirmed, you can consider the check-in/out time window to be locked in as a part of the contractual agreement with the guest. When guests need more flexibility than you can offer, advise them where to find left-luggage facilities and perhaps a nearby cafe where they can relax until check-in. You're under no obligation to admit guests to the property if their arrival is outside of the time you've agreed to, but under no circumstances should you cancel a booking yourself (Airbnb penalizes hosts for this).
I don't find that it's worthwhile to ask each individual guest about their dietary requirements when you're only offering breakfast. Unless you're running a luxury catered resort, it's more comfortable to guests to just make a few things available that they can enjoy whatever time they wake up, or leave behind if they choose to. If something in the mix is suitable for a gluten-intolerant vegan, you've got your bases covered. Those with very unusual needs might volunteer them when they book, but such people are also likelier to self-cater anyway.
No need to ask guests whether they're OK with something that is clearly shown in your listing text and photos. Only exception is if something in their communication suggests that they misunderstood what you're offering.
In short - minimize the number of questions you have to ask guests in order to prepare for them, so that you have your bases covered for the 10% or so that don't respond in time.