10 Billions of that deficit are coming from the State paying insufficient contributions for unemployed insured people. It is a policy choice to offload those costs onto Publicly-Insured-People (excluding rich and healthy people) instead of funding them through taxes (including those groups).

The German Healthcare System also has some historically developed peculiarities that don't make much sense in today's age, but they are difficult to address without pissing people off (The duality of Private and Public Health Insurance, allowing the first one to get rich and very healthy people out of the risk pool, and then loopholes to switch back into the public system when they grow older and don't want to pay the then high prices in private insurance)

The Hospital Reform is already working to reduce costs by reducing the number of small hospitals, and concentrate them into bigger ones. (As a side effect, quality of care will increase too, since outcomes are correlated with experience)

Also more care will be shifted to outpatient setting.

Otherwise we are fighting with the demographic change. But these problems are also hurting all other developed nations including the US, where funding problems in Medicaid are also expected in the next decades

tl:dr We have problems due to the demographic change, but these are in line with other developed nations. There are some efforts to address them, but politicians are hesitant to do real reforms, because old people have the most voting power