Are there subways in operation to Beijing Fengtai District? How long it takes bus from downtown to Fengdai?

THE FENGTAI DISTRICT

My wife and I are moving to the Fengtai District of Beijing near the 4th Ring Road. Are there currently subways in operation that go to the downtown area from this part of town? I have read in many places that there are additional lines under construction through Fengtai, are there any currently in operation? If not, how long do the buses take to get downtown from Fengtai? I've been playing around a lot with google maps but want to know how accurate and up-to-date it is.

Thanks in advance for your help! Happy travels!