how do I straighten my my gate attached to the neighbors privacy fence?? I can not open the fence due to the leaning into my yard, it was working great before winter hit
I know you have chosen a "correct" answer but i do not think it is a proper solution.
It appears that both posts are moving as the ground freeze's and thaw's. If they are doing so now they will continue to do so in the future, regardless of bracing.
You will need to call for utility locates so you do not dig into a gas line or other utilities.
I would dissemble and start over. I would install two new posts, the one the fence side i would put about 18" in from the fence since you have room on the house side. You need to set the new posts at least to what frost line code calls for in you area but i would try to go as deep as you can. If the frost line is 48" then try to go at least 60". If your ground is particularly active you may want to use sono tubes and fill with concrete and even put a bell footer on your sono tubes.