Hi @Omar khayaam
You do not make it clear where you wish to get married. For the purposes of this answer, I assume you wish to get married in Germany.
In certain cases, it is not possible for a person to provide a ‘No Impediment Certificate’, for example if it does not exist in their home country or, as in your case, they have refugee status.
For such cases, there is the option to provide a sworn statement about your marital status. This is called ‘eiddestattliche Versicherung’ and can be done at the German embassy (for people who are living in Germany this is done directly at the ‘Standesamt’ marriage registry office).
The German embassy in the UK does not provide any information on this option but here you can read (via online translation) about it from the German embassy in France:
https://allemagneenfrance-diplo-de.translate.goog/fr-de/service/-/2233198?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp
You should contact the German embassy in the UK and ask for an appointment in order to provide this affidavit. They will want to see some kind of evidence that you are intending to get married, e.g. something from the Standesamt where your finacé lives that confirms you have to provide this.
Best,
Éanna