Hi @SYK,
As I am not a lawyer I cannot provide legal advice but some information about travelling with a Fiktionsbescheinigung. With the type you have (§ 81 Abs. 4) you can travel. Bring it and your expired permit with you when travelling.
Here is information confirming this from the German Embassy in India (originally in German, I translated it online):
https://india-diplo-de.translate.goog/in-de/vertretungen/-/2464364?openAccordionId=item-2464374-2-panel&_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp
Here is also confirmation of it from the immigration authorities in Berlin:
If a currently valid residence permit (temporary residence permit or national visa for long-term durations - Category D - ) is available, a fictional certificate according to § 81 Section 4 of the Residence Act will be issued.
In this case, the residence permit and all supplementary regulations (also regarding the stipulations concerning gainful employment) remain in force until a decision has been made in relation to the application. Journeys abroad and re-entry into the area of the Republic are possible with a valid fictional certificate in accordance with § 81 Section 4 of the Residence Act.
https://service.berlin.de/dienstleistung/326233/en/
Best,
Éanna