Urgent advice for marriage

[Gekko]

Hello,

I am on student visa who would like to marry to my gf who is with asylum status. We both from same country and we have been in relationship for about two years. But she moved in with me 5 months ago. We have been planing to get married since 4months ago. But my gf has lost her immigration documents which is kind of made our marraige plan delay amd it took about more than 3 months to get another immigration document back from home office. i got appoinment for interview at registory office at the end of month but my vida gonna be expire after one week of interview. We got all other docutmets with our current adress. Bank Statement, bills etc. I am a bit worried I am gonna be classed as over stay after i gave notification to Local Registory Office. Please adive me anthing do i need to prepre?
Do i need to have certain amount of money in my bank?


Please advie me for information. That would be really appreciated.