Tour: Beijing - Jiankou - mutianyu - Beijing

Yes, it's around 10 kilometers. Don't worry. You can only spend one day to walk from Jiankou Spot to Mutianyu Great Wall.
Generally speaking, you don't need to prepare extra equipment for this part.
Both Wofo Mountain Villa and Xizhazi Village are good starting points.
Maybe you can try to use the APP of Baidu Map and download the Offline Map.
The Bus no.936 takes 1.5 to 2 hours and the Bus no.H25/H36 takes around 70 mins.

Hope helpful!

How was your hike Annekathrin? I'm looking into the same route. Anyone know if this is doable in late November?

it was a great experience. we took the 916 express (the first one at 6:30, highly recommnded to start early as the zrip takes some time) to huairou final station (dont get out of the bus even if people tell you to). from there we took a taxi for ~120 yuan which brought us to xizhazi / nanjili (group2). i had it written in chinese and showed it to the driver. i can send you the file (or all files and documents i used for preparation). then we took the way up to zhengbeilou tower. i found a good gps track on the internet and so we used that. if you use open street map, you also see the path there.
the hike was fantastic. we didnt do the oxhorn and used the small path along the wall instead. in mutianyu we walked down to the busses. at the ticket office you need to buy a ticket for the shuttle bus (10yuan). after 5 minutes we arrived near the roundabout. we walked to the busstation and took one of the local busses back to huairou.

regarding your november plans someone else has to answer that question.

i mean, dont get out of the bus before you reach the final station in huairou. 😊