Something to note. This doesn't happen quickly with most dogs, and testing your progress can quickly undo any progress you have made. Take your time and set the dog up to be comfortable. This can take months, but it's worth it.
If you have to take something away, try and trade for a high value treat for a while, until the dog is non reactive to you while eating. This will help enforce the fact that you are the bringer of things, not the taker that needs to be driven away.
Many think you should just wade in and show the dog who is boss, and it will work with some dogs (and some people), but it could also make your job much more difficult. JMHO
When a dog saves the life of a man, it becomes clear that partnership knows no bounds.
Fama - T.E.D.D. OEF XI-XII (GSD)(RET)
Marshall - T.E.D.D. OEF XII-XIII (Lab)(SF EDD)
Lucian - Med Alert / Mobility SD (Cane Corso)
Pud - the old man (Pit x Lab)