The USA also bought Alaska from Russia, but if they don´t want to sell they don´t want to sell.

You've read how Denmark did forced sterilizations to Native Greenlanders, right? How about this quote from "The Danes don’t see us as humans,” Amarok Petersen told The Post in a local Inuit restaurant overlooking Nuuk’s famous fjords. “They think we’re too expensive, too small a population. But they take our land, our children, our lives and expect thanks.” She was talking about Denmark taking the Inuit's children away for adoption or institutional care — often permanently separated from their families, she said. The program, which ran from the 1950s through the 1970s, was part of Denmark’s broader effort to assimilate Greenlandic children, often without parental consent.
The Denmark "owns" Greenland, not the Inuits.

No I have not read that.
But 1) Like you said it stopped 50years ago
2) it has nothing to do with their willingness to sell part of their country to the USA.

The Danish government isn't excited to sell the colony. Do a search for what the citizens of Greenland (even the ones Denmark has made into second class citizens) are saying. The European political class is the greatest opposition. Thanks for your attention to this matter.

🚨 BREAKING: European Union officials are BACKING DOWN from their retaliation against President Trump's Greenland acquisition ambitions, prefer "negotiations" rather than escalating - NYT

LMFAO! Big, Tough EU lasted about 24 hours 🤣

EU is about as feckless as NATO. . .

The German reconnaissance team that arrived in Greenland on Friday is departing the Danish territory as planned.

The heroic 44-hour German mission in Greenland has ended.

The last time Germans went somewhere that tended to be cold most of the time they got their asses handed to them.