There is no correct word about '만냥'. The correct word is '마냥'
마냥 is 'always' and 'forever' in positive situation. It is used before the verb.
I like to watch TV and I feel very relax to watch TV in weekend.
My friend says to me, "뭐해?"
And, I can say "나? 마냥 TV 보는 중이야."
I fall in love somebody and I am happy just to see that somebody
Then I can say, "나는 마냥 그 사람만 봐도 행복해"
When I have a many times, I prefer to wait someone and I will also wait somebody. then I say
"나는 마냥 기다리고있어"
"그사람 어때? " ;
"마냥 좋아!"