Some changes in hierarcy gone after i run play mode ?

i dont know what wrong ..

in first scene ,, i add some model in hierarcy ,, and i run play game mode ,,hierarcy work save my model ,, but problem a add again model or etc to hierarcy and click play mode again ,, model and other changes is gone ,,,, and refer back to (like undo) only save my model in first changes ,, i see in my project folder properties in explorer it show read only ??

help me ,,how to make unity not save my project or scene in read only mode?