When I add Fontworks to a slide, save it in pptx and then open it at my office (MS 2010) it has changed entirely and sometimes I have a problem even opening it.
Thanks for any help
I see your problem, but what is the question you would like help with?
LibO works hard on matching the always changing MSO formats. The problem is that MS does not follow the international odf-standard and has even formatting problems in their own versions of MSO.
I recommend to file a bug report here https://www.libreoffice.org/get-help/bug/
Additionally I recommend to stay as long as possible in LibO’s native format, next export to pdf and only if there is no other solution, save in a MSO format.
An interesting document to read is https://wiki.documentfoundation.org/Feature_Comparison:LibreOffice-_Microsoft_Office