You can mute the audio component of a video clip so no sound is heard by setting its volume to 0%. When you export your project, the sound of that video clip won't be included, so it will essentially be deleted.
To learn how to mute a video, see: changing the volume of a video or audio clip.
It is not currently possible to separate or extract the associated audio of a video file (the grey track that shows underneath it in the timeline) in your Create project.
You can replace the sound of a video with the sound of a different video (or with an audio track) by muting it and then putting the video or audio clip with the sound you want in the track below it. This way you will see the top video clip while only hearing the bottom video or audio clip. To see how timeline tracks work, check out our article about working with the timeline.