I have made a mistake when filing Form3520, what will be the consequence and how can I correct that?

[pk]

What kind of mistake ?  Name of Alien? country involved? amount ? or ?

Only if the amount in US$ is wrong then perhaps you should consider filing a new 3520.

[spacey1]

I thought it was a straightforward case and didn't consult with a tax professional. I received a cash gift from a foreign friend to help with a personal situation so I just filled out #54, not #55 nor #56. I then realized the funds actually came from a foreign corporation and my friend had also changed his mind and wanted the gift to be a loan instead, likely with no to low interest. It seems like I at least had made two mistakes: 1. the information was not correct on the form 2. i actually didn't need to file this form at all...

[pk]

I would leave it alone  for two reasons:
1. Don't think you can go back and withdraw  /negate a filing -- explanation will not be easy
2. If you call it a loan ( secured or otherwise but you are required to pay back ), then zero or below market interest  would trigger an imputed  income -- it is like cancelled debt ( taxable income), even though you actually go no money.
If this was just a hand-shake deal, then just let the sleeping dog ...