public class OrderTest {
private WebDriver driver;
private String baseUrl;
private StringBuffer verificationErrors = new StringBuffer();

@Before
public void SetUp() throws Exception {
    System.setProperty("webdriver.gecko.driver", "C:\Users\egor\Documents\geckodriver.exe");
    driver = new FirefoxDriver();
    baseUrl = "https://www.natalie-tours.ru";
}

@Test
public void TestOrder() throws Exception{
    this.driver.get(baseUrl);
    this.driver.manage().window().maximize();
    WebElement countries = this.driver.findElement(By.id("countries"));
    countries.click();
    Select dropdownCountry = new Select(countries);
    dropdownCountry.selectByValue("18");
    WebElement myChosenCountry = dropdownCountry.getFirstSelectedOption();
    myChosenCountry.sendKeys(Keys.ENTER);
    String parentHandle = this.driver.getWindowHandle();
    WebElement selectZone = this.driver.findElement(By.id("zones"));
    selectZone.click();
    Select dropdownZone = new Select((selectZone));
    dropdownZone.selectByValue("16");
    WebElement myChosenZone = dropdownZone.getFirstSelectedOption();
    myChosenZone.sendKeys(Keys.ENTER);
    WebElement searchButton = this.driver.findElement(By.cssSelector("input[type="submit"]"));
    searchButton.click();
    Thread.sleep(10000);
    Set<String> windows = this.driver.getWindowHandles();
    System.out.println(windows.size());
    Iterator iterator = windows.iterator();
    String currentWindowId;

    while (iterator.hasNext()){
        currentWindowId = iterator.next().toString();
        if (!currentWindowId.equals(parentHandle)){
            this.driver.switchTo().window(currentWindowId);
            WebElement buttonOpt = this.driver.findElement(By.xpath("//*[@id="moreInfo1293951883"]/button/span"));
            buttonOpt.click();
        }
    }

Thread.sleep(10000);

}

private boolean isElementPresent(By by) {
    try {
        driver.findElement(by);
        return true;
    } catch (NoSuchElementException e) {
        return false;
    }
}

private boolean isAlertPresent() {
    try {
        driver.switchTo().alert();
        return true;
    } catch (NoAlertPresentException e) {
        return false;
    }
}

while (iterator.hasNext()){
        currentWindowId = iterator.next().toString();
        if (!currentWindowId.equals(parentHandle)){
            this.driver.switchTo().window(currentWindowId);
            WebElement frame = driver.findElement(By.id("STD_SEARCHER"));
            driver.switchTo().frame(frame);
            WebElement buttonOpt = this.driver.findElement(By.xpath("//*[@id='moreInfo1293951883']/button/span"));
            buttonOpt.click();
         }
    }