Its actually easier to send it out of our solar system than to the sun. And then there are the other reasons like limited capacity of rocket, costs, failing rockets, amount of waste etc.

why can't we launch the waste to the sun?

Because we are talking about thousands of tonnes of highly radioactive waste (not counting the lower ones). A quick search tells me in the region of 15.000t for Germany. That alone makes it pretty expensive.

And then you want to launch it into space where every start you risk an explosion that spreads that waste?

That's a huge waste of energy.

If the "waste" is "highly radioactive" that means that is has A LOT of energy left in it. It should be reprocessed, recycled, and should provide power for another 20years. The whole idea of nuclear waste needing billions of years of storage is just propaganda to ensure nuclear reactors are never a threat to the existing fossil fuel markets.

By the way despite a huge increase in the amount of "green energy" produced by germany last year, they have also burned more fossil fuels then they ever have in history, same story in China, the US and other European countries.