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#1
On the security tab, click the advanced button and change permissions from there.
There is a checkbox that says "replace all permissions on secondary objects" that when checked puts the same permissions on each file to be the same from the containing folder.
Probably you need to take ownership beforehand. Use owner tab on that dialog for that, and check the appliy for all option there. Then try again.
Selam neighbor,
I guess it is just a warning about closing the properties and re-opening. Click OK then close properties. Open properties again after closing all and see if the owner is changed.