Slow motion problem

Hi I shot x mistake a video (go pro) with the slow motion mode already active.
Once imported to Fcpx the video is slowed down except the beginning and the end. If I try to change the speed of the video and put it at normal speed I can't get "normal" audio but I only have a muffled sound
Is there any option x that once you put the video at normal speed you can also have the original audio of the shot?
By chance I did it by tweaking some audio settings like the Speed Ramp but I didn't understand how to do it again
Does anyone know how to do?
Thanks in advance

I don’t understand what you mean with mistake?

Regarding the slow motion not being effective at the beginning and at the end of the clip: make sure your video isn’t already set with a speed ramp from the camera.
Also was this when you add a speed ramp to the clip or do it play like that in the browser?
Next time just record your footage in a higher frame rate.

For the audio just break it away from the video then you can manipulate both.

I said mistake cause I didn't want that speed rate setting, I just wanted to make a normal video and then make the slow motion on fcpx. But with with the settings that I had on my camera when I shot the video, all the video was already in slow motion.
Anyway I have to change my settingsthe speed rate on my go pro thanks
About the audio you said that I can split it from the video and then I could manipulate it right? how can I do it?