Overwrite existing files in fileadmin isn't possible with Internet Explorer 11 due to a CSS bug
If you upload a existing file in the fileadmin TYPO3 with Internet Explorer 11 it shows a message to overwrite and confirm the new file. Due to a CSS Bug the upload can not be done due to a CSS error. See printscreen.
As described on the requirements on typo3.org the Internet Explorer 11 should be supported.
TYPO3 version 8.7.2