Hi Cathy
'does my writing SOUND natural?'
'it's been a long time to have one of my favourite...'
Based on the context, it would appear that you are describing a period of time in which you have enjoyed Dak-kalguksu. On this basis you would say 'it's been a long time that I have been having one of my favourite foods.' Here you are describing an activity that started in the past and continues until now.
structure
subject + have + been + 'ing
... 'so I'm gonna sharing' - 'gonna' is an informal way of saying 'going to'. Either way you would follow both of my examples with the infinitive verb
'for someone who currently stays in Korea'.. grammatically it's unclear; it sounds like you are talking a particular person who maybe you know and they generally stay there (maybe for business or fun). My guess is you mean if someone was going to visit? On this basis 'for someone who is going to stay here.
'Big recommendation as a local resident' would be better replaced by 'I very much recommend this place.'