Dear @Juwwel51,
Welcome to the Wefugees Community and thank you for reaching out to us.
First of all, I want to highlight that I am not a lawyer and that you did well in contacting one in this rather complicated matter. Immigration law in Germany is definitely not easy to understand and often similar appearing cases are assessed differently by law implementing authorites.
That being said, I wanted to ask you about your status in Italy. Are you holding any kind of temporary or permanent residence permit there (which may allow you to visit another Schengen country for up to 90 days without a visa)?
I believe that you can get an appointment at the Standesamt (registry office) without a valid visa. However, (as my colleague Éanna explained here - be aware that the respective case constellation is different as the future spouse was an EU-citizen, not German) "as part of the process, the authorities will be made aware that you are in Germany without a legal status. For such situations, authorities such as the registry office and immigration office share information."
Well, as you are registered already, the authorities will learn about your presence in Germany anyway, though. My colleague explains further: "If the requirements for getting married have been met, then [you] can be issued with a temporary residence paper (this is not a full residence permit) called a ‘Duldung’ to allow [you] to stay in Germany to marry." This is what your lawyer explained as well, right?
From what I know, when you managed to actually get married (please see also our blog in German and English on this topic), it is likely that the authorities will ask you to apply for a respective family reunion visa at the German embassy (either in India or possibly also in Italy, in case you have a valid residence permit there).
It is rather impossible for us to understand if your lawyer is trustworthy and experienced in migration/immigration law. If you have doubts, it might make sense to contact a migration counselling office for some support. They offer their services free of charge and confidential.
Furthermore, we can not give any estimation on the duration of the whole process. Unfortunately, many registry offices but also immigration offices are understaffed and overwhelmed with work in these days - waiting periods can be quite long.
I hope my thoughts are helpful and please don't hesitate to get back to us with any further questions and/or to keep us updated.
All the best,
Meike