Decommission Spartec heat pump

Good day,
we want to decommission our Spartec heat pump with surface collector.
Now we have the problem that we cannot find the outlet for the coolant. Perhaps someone can give us some tips?
The brand was only produced for a short time and installed rarely, the manufacturer has not existed since 2008.
The manual only states that it must be done by specialist companies.
An unknown brand is too complicated for most companies.

Best regards
Steffi

If you want to drain the coolant, you need someone with a refrigeration certificate. You have no business doing it yourself!

Good day,
I do not want to do it myself. So far, no craftsman has been able to find the spot. Therefore, I am hoping for tips on where it is so that the craftsman can continue.
Best regards