Hundreds of billions have already been spend on learning renewables in Germany.
https://www.researchgate.net/publication/321765366_How_expen...
https://www.researchgate.net/publication/321765366_How_expen...
In term of decarbonization of electricity production and independence of imported fuel for electricity production, it got less then France for comparable amount of money.
But this is quite clear as the first and foremost goal of German Energiewende was denuclearization of German electricity production, not decarbonization of electricity production.