Take a look at this. To change the text in the second field, Javascript needs to be utilized.
I provided options for three choices, but adding the remaining two should not be difficult.
Keep in mind that countryInput.value returns the "name" of an option, not the text displayed.
For further clarification on how the Javascript functions, there are other resources available besides stackoverflow.
function cityChange() {
var countryInput = document.getElementById("country");
var cityInput = document.getElementById("city");
var city = "";
switch (countryInput.value) {
case "france":
city = "Paris";
break;
case "slovakia":
city = "Bratislava";
break;
case "germany":
city = "Berlin";
break;
}
cityInput.value = city;
}
<select id="country" onchange="cityChange()">
<option disabled selected> -- select a country -- </option>
<option value="france">France</option>
<option value="slovakia">Slovakia</option>
<option value="germany">Germany</option>
</select>
<input type="text" id="city" readonly/>