The following statement has been taken from the Internet:
‘We are waiting to help you building your strong future.’
As far as I know the following structures exist in the grammar world:
a) to help do smth;
b) to help to do smth.;
c) to help smb.do smth.;
d) to help smb.to do smth.
I have a question:
''to help smb.[b]doing[/b] smth." - is it an informal grammar structure?
That structure is not possible (the sentence you quote from the Internet is wrong).
The only way that example could be correct would be if it were read like this:
We are waiting to help you while you are building your strong future.
If that is not the intended meaning, then the example should correctly read:
We are waiting to help you build your strong future.
As ‘strong’ also seems a strange word to use there, I suspect the example is wrong and was likely to have been written by someone who does not speak English as their first language.
‘Secure’ would be a far better word.