Blur the background behind a moving object

[deboopi]

Hi,
I found out how to blur parts of a video but I'd like to know how to keep a moving object sharp and blur the rest of the video.
I'm filming with a smartphone and despite the lens opening you still have the entire surface sharp.
My daughter is attending figure skating and on competitions I'd like to have her sharp in the video and the rest blurred.
I already tried adobe premiere, adobe after effects, wondershare filmora and dozens of other software but they all have problems with the moving object .
In the entire video they always miss too many frames.
The video is 60 frames/second and lasts about 2:30, so that's a lot of frames to go through for correction afterwards.
When searching for video editors I now also found this forum to look for help.

[poisondeathray]

You would have to isolate the foreground object (daughter), by masking or rotoscoping . The rotobrush in AE can help, it's semi automated. It can be very time consuming if you want it accurate. Composite the sharp layer over the blurred layer

"miss too many frames" - it's possible that your smartphone recording was VFR (variable framerate) and dropped frames. ie. your phone missed to many frames leading to gaps in motion