Hello AdityaRahman,
Welcome to OpenStreetMap! Please follow some practices while editing on OSM.
Avoid adding duplicate data, zoom in to make edits to avoid any overlaps, for buildings, draw from the building edge.
Please watch this video - https://www.youtube.com/watch?v=E1YJV6I_rhY, this will help to start.
Please square the buildings (use Q from the keyboard) when it is needed.
Do not ignore the validation warning messages.
Happy Mapping!
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Published using OSMCha: https://osmcha.org/changesets/169335906