I didn't answer this question. I don't know the answer, not exactly. It depends what proof you had that you were both there and have visited each other, etc.
But crucially we didn't see your file and know the details - you should know better. If you were both there, this should not be hard to prove.
It would be worth looking at other parts of your application, too - it seems it was not good evidence that you had spent time together.
If you have good evidence, you may not need a lawyer. If the file is fraudulent, a lawyer is probably not going to help.
If this is still unclear to you (that is, why the file was considered weak) - then you might need a lawyer or a good consultant.
This might be very important, this last point: if you don't understand, there's an issue, because IRCC clearly thinks the file is fraudulent.
I wouldn't even guess what the chances of success are, not without knowing the underlying issues.
