file do not update explorer <> DW

That's definitely not something DW and your OS should be doing. Typically, DW just works with files saved on your operating system. If a file is changed at the OS level, there's nothing in DW that would hold onto the old information, aside from maybe some kind of versioning workflow, like Git, maybe?

Is there any chance you have accidentally duplicated your pages and aren't actually working on the same exact files? 

The above happens pretty regularly when using DW without a Defined Site, or when the site hasn't been defined correctly. Many times, what happens is a duplication of the site's root folder (www or htdocs) in the local copy due to a settings issue. When working from within the site, it's updating a duplicate file within a duplicate root folder. When working from the OS, you're drilling down to the correct file (usually one directory above what DW is seeing).

Check your site files from within DW. If you see "www", "public_html" or "htdocs" inside your Files window, you're likely looking at a duplicate set of files.

Where are you making the changes? The way I read it, you make the changes in the browser. In this case the changes will not have been saved.

If I have misread the post and you have made the changes in Dreamweaver after which you do not see the changes in the browser, then you need to empty the browser cache. Maybe refreshing the browser a couple of times by pressing F5 will help.