As often you are talking about things you only partially understand.
Yes, some lakes are acid at the beginning, that's not unespected, but they are far from "ecological dead" and a normal pH can be (and is) established with some maintanace.
Situation when flooding just started in the 90s: http://www-docs.b-tu.de/fg-gewaessersch ... 2_ar_3.pdf
Situation now: https://www.lmbv.de/index.php/guete-von-lmbv-seen.html
17 out of 30 lakes already have a good water quality just a few years after flooding them.
(and btw, of course you can bath and swimm in those lakes, also in those where it isn't allowed yet. Obviously at your own risk in such cases.)
I'm heavily opposed to talks about burning huge amounts of lignite until 2040 or even 2050 (maybe keep some power plants as a "cold reserve", if technological possible), but on the other hand the global climate is already fucked anyway. Tar sands in Canada, gas fracking in US, deep sea oil in the gulf of Mexico, lignite in Germay, None(!) of that stuff should be allowed to be burned if you really care about limiting global warming at +4K.
+2K has already become complete utopia no matter what we do.
But I'm also opposed to nuclear power plants in Germany. If the US or China wants to build them that's not my problem, as long as they are far away and as long as they pay for a reasonable" waste managment of their radioactive stuff.
Having one reactor melting every 10.000 reactor years so far translates to an average time of 25 years between catastrophal events now with ca. 400+ (aging) reactors in the world. I visited Chernobyl last summer and I don't want to have something similar in Germany.
And this accident rate and the generally super high costs of nuclear power generation, the still unsolved problems (after 60 years!) with waste managemnet and the risk of proliferation to terrorists is for only 2% of global energy demand! To make an impact on the energy sector the world would need at least 10 times more nuclear reactors!
Who would pay for them?
Where to get the uranium?
How to avoid proliferation?
What to to with an dramatic accident every 2.5 years?
It's a good idea to avoid that nuclear shit in Germany asap especially at times when noone(!) in the world has shown any interest in really limiting global warming.
Germany (together with a handful of other countries like US, China, Denmark, Spain) paid billions to make solar and wind energy cost effective for the rest of the world. That's already much more than what most others have done so far.
So nuclear shutdown first (because this is the highest risk) and coal shutdown second. (Maybe keep an reserve, because situation to Putin's Russia and Erdogans Turkey needs also be considered for natural gas import security)