Miltoniopsis bought sick already, wanna save badly!

[Su7Seven]

hi all,

my first orchid of this kind makes me sad everyday. As a newbie, I did not know what to look for to recognize sick plants. Her Bulb was shriveled, I thought I water today and it will be ok. But it was not.

The roots were firm but came off, and inside is a hairthin dry root. The soil was very broken, muddy something. I repot it in spaghum, in pine bark with perlit and leca.

She became worse. So one after the other leave yellowed. All can see at: https://youtu.be/CxaA1L5ALl0

I end up with sweet ugly smell. Took it again from potting mix, cut some roots off. But the smell unbearable. I used peroxide and cinnamon. Trying everyday to save her. Now she ist just in plain water. Slightly wraped up opening of glass. Every day wetting her one leaf left. So sad so sad.

There are black spots though! I cant remove it. Ok now it smells little, but what to do with the black spots? shall I leave them? cut off? how much? where?

Some said dont move it around it cant root that way. But I have to clean the roots, three times a week?
I wont buy another one to replace, I want to save this plant! I want to understand, what is happening, solving problems.

thank you