You should be able to pay for access to the airport business lounge, if you want lounge access and do not otherwise have it (Priority Pass, status or J class); details should be on the DME airport website. There are also a number of airside food options, and as noted free WiFi. As others noted, while the airport may be crowded, it should be fine. There are airside bank machines of you want RUB, though most eating establishments should also take cards.