I can't correct mistakes on the multitrack.

I think you need a little more understanding of how Audition works. Multitrack view is non-destructive - it's posh file player, but it can't edit your actual file. What you have to do is make selections of the bits you want to cut out, by dragging the ends of the selections you've made (using the split function, if it's all in one file) and move everything else up to meet the joins.

But you can't really take out sibilance like this - that's a process effect that has to happen in Waveform view. There's nothing to stop you removing sections destructively from a file in waveform view, but if that file is already in use in a session, you'll get a warning because potentially, your removed sections could result in anything you've already placed not being in the correct position any more. That can't happen if you move stuff in Multitrack, because you haven't touched the original file, and the session file keeps track of what you are playing, and where you've placed it on the timeline - it's altering the original material that causes the difficulties.

For you, probably the best approach is to record in Multitrack, open the file in Waveform view and do any sound corrections there - you can save these, so you'll end up with your original file still, but with whatever non-temporal alterations you made. Then go back to Multitrack, split out the bits you want, and rearrange them there. The advantage of this method is that you'll still have an intact original file, so if you need to go back and change things, you still can.