What are the differents of these suffix "-hapnida, -hada, -haeyo, -i, etc..."
Thx for your help..^^

Question

What are the differents of these suffix >> "-hapnida, -hada, -haeyo, -i, etc..."
Thx for your help..^^

Answer

Study 
Gongbuhada : basic form of the verb
Gongbuhanda : the present tense of the verb
Gongbuhamnida : formal＆written Korean style 
Gongbuhaeyo : informal＆spoken Korean style

I don't feel familiar with the formal style. So it's better to talk in the informal style(Gongbuhaeyo) when you talk with Korean friends.  

I have no clue about -i if you didn't mean the postposition used after nouns end with one or double consonant. Could you elaborate a bit more?