problem
If I wish to trim a long blank intro to allow the song to start sooner, i tried highlighting the portion of that file and I hit delete…the entire file disappears.
I’m set to destructive editing.
What am I doing wrong?
cut would get rid of unwanted area,
but you would still have to grab the left edge of the file and slide it to the left for the song to start earlier in time. 
dontcare 
I Very seldom use the destruct edit. Non-destruct will do everything except permanently change the wave file forever.
As to shorting the file Dontcare gave you the answer. Once the file is shortened, you can drag the file to the left to the start point.
If you have several track, you can highlight/select all the file and move them at once without losing sync. Once the track is shortened, you can also do you mixdown and start it from the new start ( highlight/select the section you want to mixdown
So in non- destruct edit, I can use the same method to trim the end of the file as well?
sure