Present progressive and "I'm going to" difference?

[Michauek]

I have read somewhere that there is no difference between "I'm going to" and " I am doing" , but i think there is a difference

for example :

I'm organising a party tommorow. (i'm organising, means i've done smth to organise it??)

I'm going to organise a party tommorow. (just planning to organise ?? )

Is there anny difference between these 2 sentences?
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Experience is the name everyone gives to their mistakes. Oscar Wilde
Michal. I'm an english student

[Mister Micawber]

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Both the present continuous and the 'going-to' future are used for future events. The present continuous usually indicates that the plan is firm, the future occurrence is near and inevitable: 'I'm meeting him at 7:00'; I'm visiting my aunt in Honolulu this summer'.

The 'going-to' future also indicates the speaker's determination of the inevitability of the event, usually based on present knowledge of some kind: 'It's going to rain tomorrow' (the weatherman said so); 'I'm going to meet him in St. Louis' (a scheduled event).

As you can see, the uses are quite similar, so there is often little or no difference in the speaker's intention when using one or the other.

In your example, however, there is a problem of ambiguity: is the party tomorrow, or merely its organization? If the party is tomorrow, then your first sentence indicates what you are doing NOW and your second sentence is odd (it will leave you precious little time to get organized!). If the organization is tomorrow (for next week's party), however, either sentence will do, with essentially the same meaning: a solid plan to organize in the near future.
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Native English teacher at Mister Micawber's

[Michauek]

"I'm organising" I meant that "I do" a party tomorrow , that tomorrow will the party started. For example:
One day before the party -> "Hi Jim. I'm organising party tomorrow. Would you like to come? "

I am confused now :/
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Experience is the name everyone gives to their mistakes. Oscar Wilde
Michal. I'm an english student

[Mister Micawber]

"I'm organizing a party tomorrow"

If the party is tomorrow, 'I'm organizing' means today.
If the organizing is tomorrow (for a later party), 'I'm organizing' means tomorrow.
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Native English teacher at Mister Micawber's

[Michauek]

oh i see. this was a misunderstanding because when we I say "I'm organising" I mean I'm doing it at the moment (a party) .
Thx a lot !
_________________
Experience is the name everyone gives to their mistakes. Oscar Wilde
Michal. I'm an english student