1. Audio clips that are mono can only be placed on mono tracks, stereo on stereo tracks, etc. If you want to add audio tracks to get the right kind of track into the first track, it is easy enough to do so.
2 Yes, it happens to me sometimes as well. Click on the transition and change the setting to “center on cut” in the Effect Controls panel. It may be that you don’t have heads or tails trimmed properly, or it may just be stubborn.
3 Adding to the end of the sequence is a simple matter of moving the Current Time Indicator (CTI) to the end of the sequence before you insert or overlay. To add something to a different track, select the track before you insert or overlay.
4 There are a lot of tutorials available, but you might want to pick up a book (shop at the Dairy Store here at the COW to be a good citizen – top of this page has a link to “Store”). There are a few podcasts and tutorials here as well.
Steven
https://www.stevengotz.com