We have found one software suitable in our database for this conversion.
You actually cannot convert gslides to pptx, i.e. convert Google Drive presentations to PowerPoint presentations.
However, when you open your .gslides link in Google Drive to access the Google Docs document, you can download the file in PPTX format using the File ► Download as function in the upper menu. This gslides to pptx conversion is good when you want to continue to work with the presentation in Microsoft Powerpoint.
GSLIDES
Files with gslides file extension are URL links to a presentation created in Google Drive. It is not the actual presentation, just an URL link. You can download the presentation from Google Drive in more typical format, like PPTX or PDF.
PPTX
Files with pptx extension are presentations from modern version of PowerPoint from Microsoft Office / Office 365. PowerPoint slide shows are basically set of screens which can include text, graphic, sounds or videos used for various presentation purposes.