When the soffit was installed, a length of support channel was nailed to the wall. The inner edge of the horizontal pieces rest on the channel.
From your photo it's clear that the support channel is no longer attached, which is allowing the whole assembly to sag at the end. Who knows why.....maybe something has rotted and the nails have pulled loose. It's possible that there's been a roof leak just above where the roof slope meets the side wall (are you in snow country?). If so, that's going to need attention or there will be more trouble in the future
It's going to be necessary to remove some of the horizontal pieces in order to see what has happened. Some corrective work will probably have to be done so that the channel can be be nailed back in place. Once the situation with the channel has been fixed, then of course the horizontal panels will go back in place.
GrayFlannel is right.....hire somebody.
But don't hire somebody's layabout brother-in-law who drinks too much and is bluffing about being able to fix it
here's a photo of something similar so you can see what the channel situation looks like: