Welcome!
Glad that you mention it.
There has been a lot to do about trees and imports:
https://forum.openstreetmap.org/viewtopic.php?id=59806
https://forum.openstreetmap.org/viewtopic.php?id=58126
https://forum.openstreetmap.org/viewtopic.php?id=59371
edit 23:27: If you are new to OSM than it is not a good idea to start with a large project. It is best to map your local neighbourhood.