When we already talk about Fraunhofer, they with a few other institutes, have been sketching out various pathways over the years for Germany for transitioning to a renewable energy system multiple times, see https://langfristszenarien.de/enertile-explorer-wAssets/docs...
While Germany has some hydro, it's just a tiny amount
In pessimistic economy growth scenario about 80GW of gas are needed or more otherwise. The hope is to sometime replace it with hydrogen which looks like a gamble https://ieefa.org/resources/germanys-gas-and-hydrogen-gamble
again my remark: I don't know how you read this out of the report:
> If you dont like nuclear and have no hydro, it basically means fossils
The report doesn't even aim to make claims about feasibility of energy systems without nuclear, natural gas and hydro power.
> In pessimistic economy growth scenario about 80GW of gas are needed or more otherwise.
1) during the specific paths of which there are infinitely many ... (including the ones I linked)
2) seldom usage
3) replaced over time (when extrapolating there would be no natural gas usage )