do i need to start missions from starting point for it to count ?

cause few days ago i did 3rd mission till alpha point(legendary) and quit,then yesterday i played some other missions in campaign
today i started from alpha point got to the end(legendary) and it didnt count o.O

You messed it up. If you do one mission, then quit and do another, data from previous is lost

took me like 1h20mint o get from alpha point to the end
shit is hard and boring

ill help u get through it if ur not doing it solo and i had the same problem u did with it not showing up so i did it from beginning to end with no breaks and it showed up completed on legendary

im trying to do it solo cause i dont feel like playing twice on legendary

can i do it in split screen ?

it wont count as solo campaign if u do it splitscreen