No mistake should take hours to fix. Immediately press <ctrl-Z> (EDIT | UNDO) to backtrack, step-by-step. Of course. Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. Then you can restore a project to the state it was in when saved. Just double-click the VPJ file (which isn't playable).
If a clip is added to the head of a series of clips (with no gaps) those clips will be pushed to the right. No gaps will be created. You may have inadvertently created those gaps.
In this demo the 'smile' was added to the head of three stills. Though it may appear that there are gaps, that's just the nature of the thumbnail display. Switch to Storyboard mode, where true gaps are easily seen.
Record_2020_09_27_08_22_37_820.mp4