40% of our electricity comes from renewables already. And it would be much higher, if the Energiewende ("energy turn (to renewables)") hadn't been sabotaged by the same parties that wanted to use coal and gas (namely CDU and SPD).
If 40% of that was renewable, that puts renewables' portion at around 200 TWh
It's hard to find consolidated recent figures for German electricity storage capacity, but everything I can find lists it in double digit GWh at most, including battery and pumped storage capacity. https://www.hydropower.org/country-profiles/germany https://www.energy-storage.news/germany-growth-in-home-and-i... https://www.energy-storage.news/residential-segement-continu...
So there's clearly some creative accounting going on behind that 40% figure. Maybe it's 40% of raw power produced that then gets exported and pays for other sources or something, or maybe that 40% is strictly during the day and can't be replicated at night. But it's clear the storage necessary for a completely renewable grid is lacking by multiple orders of magnitude.
Of course, you need baseload power generation for non-peak power, and DE really should have stayed with nuclear for that instead of pushing coal/gas.