Maps.me：
if you have no mobile network traffic, Maps.me will be your first choice, which is GPS mode. you need download the Beijing maps beforehand.
WeChat APP:
because WhatsAPP is not work in beijing, and most chinese use the WeChat, it would be easy to use the WeChat to chat with chinese, the WeChat has the English version, and translation function. it means you could chat with any chinese by mobile.
or you could download any translation APP which have chinese translation function.