Additional the German power grid is super stable, black- or brownouts simply don't happen.
> This causes the electricity price to routinely go negative because our neighboring countries don’t want to have it either.
This has and probably will always happen. For example Aluminum smelters are getting paid to burn electricity almost since the beginning of the industrialization, otherwise this industry wouldn't exist.
> What a failure. And what a failure that people still fall for that exportweltmeister lie
So building up massive renewable capacity while starting to sell more and more of it is a failure to you? Either your expectations are crazy high or very low...