All gears are going one over to the right
As Criggie said in his answer you basically just need to adjust both the front and rear derailleurs. This is well within the capabilities of a home mechanic if you know what you are doing. Trick is knowing about limit adjustments (prevents the derailleur moving too far in or out) and indexing adjustments (aligns the derailleur over the sprockets or chainrings. What really helps is a article or video that walks you through the process step by step. Park Tool has particularly good ones that are clear and easy to follow.

Rear derailleur (do the rear first): https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment

Front derailleur: https://www.parktool.com/blog/repair-help/front-derailleur-adjustment