For the price it will take to do this in post, you could greenscreen, 5 minutes later after key, drop fading foilage in and be finished. But for the sake of argument, let’s try the hard way.
After you have perfect mattes which I discussed in the above post, you will still need to clone the missing layers by creating a special type of clean plate that you don’t see in the beginning of the effect, i.e. they’re hidden.
There’s so many tutorials covering all the skills needed that I either post 100 links or post none. Needless to say, unless you’re absolutely sure you can finish, I recommend greenscreen. It will be better faster, cleaner, and more tweakable.
https://technicolorsoftware.hostzi.com/