Hi, as someone who has a close family member diagnosed with depression: my only advice to those suffering, please build a support system and ask for help from professionals. Your support system could consist of your family and friends, and it could just be your friends, or it could just be your family. It's whatever works for you.
And for those on the outside: please be understanding. This shit takes a long time and for much of it, you most likely won't hear what they're thinking about. Respect the fact that they have other people to rely on outside of you.