Dear @Kesskester28
Welcome back to the Wefugees Community and thank you for reaching out to us again!
I am afraid, though, that I can not add much more information on this topic than in my answer on one of your previosly asked questions. The immigration office CAN (as far as I know, they are not obliged to do so) issue a pre-approval letter ("Vorabzustimmung" according to section 31(3) AufenthV) for someone who needs to apply for a visa at the embassy in his/her country of origin and who has profound reasons to keep the whole procedure as short as possible. The conventional family-reunification process prescribes that the immigration office will be involved AFTER you applied for the respective visa at the embassy. Sometimes it can take a considerable amount of time until the immigration office handles the case and, after having finished its checks, is giving the formal approval to the embassy (which only then can make the final decision on the application). You may save several weeks or even months "skipping" this step in case you can provide the pre-approval letter already. Please see also my colleague Alla's answer here again.
I hope this helps and good luck for the application!
Best,
Meike