There's no miracle cure, unfortunately. Keying will be problematic on the socks, the ball reflections and possibly the skin tones as well. If you must use this footage, it's going to require some tedious hand masking/rotoscoping.
Personally, I'd re-shoot.
well I didn't find the miracle cure right now but maybe there is one
Unfortunately I have to use this footage. But can't I edit the footage by using some colour effects so that it gets easier for keying? The colours don't have to be exactly the same in the end and the final clip will be used on a grey surface. So some little transparent parts – like the reflexions – are not that fatal.
Here's a quick 2 minute try at pulling a key from your still. I've left all effects parameters visible so yo can see what I've done.
On the bottom layer I used a luminance key to extract the best I could from the background. This left a lot of shadow on the floor still visible, so I used a mask to get rif of the lower segment of this layer.
On the upper layer, I used a Linear Color Key to extract the best I could. This leaves a lot of soft edges and holes, especially around skin tones - thus the two layers.
There are still obvious holes in the ball reflections that would need to be filled. It's far from a perfect result, but perhaps will work if your scale is quite small for your final output.
You're so kind That's looks quite perfect to me. I've tried the same (just with one more keying effect) in my video and it works fine
Thanks a lot for your detailed answer!!!!