Can anyone help me out?

Can anyone help me out? I have a .stl model of a humanoid with arms. I want the arms split off the rest of the model so i can print them upside down.

I have tried multiple softwares but none of them can do this as it should, or not at all. I just want to split the arms off but keep them as a seperate object.

Is there someone who can split this for me? Or provide me with some info over how to accomplish this?

Here is the model: https://www.myminifactory.com/object/3d-print-old-man-logan-45708

meshmixer /pane cut.
see: https://youtu.be/l4RCLuUwETU?t=3m42s

@Christian_Schulz Thank you. I somehow managed to remove the parts one by one, by selecting the vertices and deleting them. Then i filled the remaining hole with the ‘fill hole’ function.
Though i have no clue if this will work right and even if it will print. It seems to fix tge hole with a non linear surface.

So i will try again with your suggestion. Thanks again!

Maker’s Muse has quite a few Meshmixer tutorials: https://www.youtube.com/watch?v=C9VDKb3W4qA