I have an urgent request - we recorded an important session of multiple speakers (people) one after the other in audacity. After the original file was saved it was compressed to mp3. The original pre mp3 
deleted for legal privacy reasons. We only have the mp3 now on usb and computer windows 8. audacity latest version. on play back the speaking at the end of the service is overlapping and playing at the same time as beginning. is there any way to reverse this layered fusion of speaking people all at once. it’s a jumble. hope there is a solution,IT’S URGENT!!!
What was the “pre-mp3”? An AUP Audacity project? You should not delete those until you are sure the audio is correct. The AUP is lossless quality so you can export as many MP3’s as you like from the project and each MP3 has the same quality (slightly lossy). If you re-import your MP3 to edit it again then re-export it, the re-exported MP3 is worse quality than the original MP3 you imported.
If these are multiple MP3 files, use Time Shift Tool (F5) to click and drag each one where you want it to go. If you have only one MP3 then (from your description) there is nothing you can do without the original project. You cannot unmix audio that has been mixed together.
Gale