how can deselect categories from ” uncategorized “

You can do a “Bulk Edit” from the post listing screen in the admin. Tick the posts you want to edit and then from the actions dropdown at the top of the table choose “Bulk Edit” and click apply. You can then make the same changes to categories and tags etc. for all posts.

You can also use the screen options at the top right of the screen to show more than the default 20 per page, allowing you to edit more at once in bulk.

??

boring

if u have 500 posts

it should be easier way

You could of course write a script / function to do this as well but that would be a little more complicated I think.

I would recommend doing 50 at a time.