I have several PowerPoint presentations that I can't open them now it says " file may be corrupted when
using PowerPoint or expansion
file may not match the internal file format " . Please
help, I these presentations have been using them for a long time, I need help how to recover data?

Usually, there are two way you can try to recover your former power point files.
First one, check the AutoSave. For our computer, when files such as Powerpoint and Word corrupt, it will AutoSave the files. Although not the all of the file. The premise of AutoSave is have set the AutoSave interval. The path to check the AutoSave is:
1. Go to folder
2. Choose Go, then go to folder
3. Enter “/Users/”
4. Choose your user name and enter
You will find the path “/Library/Application Support/Microsoft/Office/Office 2011 AutoRecovery”

Different version of office, the path may be different, for the office 2016, the path is /Library/Containers/com.microsoft.Word/Data/Library/Preferences/AutoRecovery/

Second, try to use the data recover tool to recover the lost or deleted files, such as documents, images, videos etc.

Good day! try repair ppt file : http://www.ppt.repair/