I need an Immigration Law Professional

To whom it may concern: I am a US citizen living in Munich with my fiancé. I am currently in 'Ausbildung' and once I am done (Aug. 2021) we want to move to the US together. I think we need help figuring out all the paperwork. I read a lot about it and it sounds like I have to live in the US to file all paperwork but we wanna move there together and don't wanna be separated for such a long time until the visa is approved. We wanna do it right and professional help would be necessary to do so. We would rather get married there (Texas) but if it's easier and faster to move there with him we could do it here too. My fiancé is Croatian citizen. I look forward to hearing from you soon. Sincerely Virginia Kobler