Audio Export Really Slow

Hi guys,my I’m trying to export as MP3 mono file but exported playback is really slow. My Mlan Sound card sample rate is set at 96Khz my project is set at 44.1Khz …I tried converting audio in C7 to match sound card sample rate still export playback is slow…Is there a simple way to fix this without having to Re-record with project set at 96Khz …
Thanks