Welcome to OpenStreetMap.

I'm not sure what you were hoping to achieve here, but I'll try to help if I can.

There's no need to add additional parks within a park which has already been mapped, as Plumstead Common is already mapped as a multipolygon relation:
https://www.openstreetmap.org/way/262748978

A park shouldn't normally be mapped as a node, but as an area. The documentation on the wiki is here:
https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dpark