It takes 20 years to build a nuclear reactor. In modern germany probably more like 40. It makes way more sense to just go full renewables.
Nuclear power is a bad combination with renewables because nuclear reactors typically are designed to provide a base load. You can't just quickly turn them off and on against depending on how much power renewables can provide. That is why renewables are typically combined with gas reactors because they are super fast.
At best we can get to like 75% renewables and 15% gas and we won't be able to come off gas for a long time. Maybe if you have so much renewable power that you can deal with the huge losses to convert the power to gas or hydrogen. Or if you have some kind of smart grid with electric cars as a buffer. But this is way more in the future.