I have seen this plant the last years in Berlin’s surroundings, always close to the water, mostly in swamps or very close to lakes. It is about one meter high, has a single stem with a diameter of ~1 cm and relatively big leaves with serrated borders that grow from nodules in the stem, several at the same height. Like here:
I ignore whether they sprout from a ryzhome or similar every year or whether they are annuals, sprouting anew from seed and I did not want to dig one out. They have beautiful flowers that look similar to the Antirrhinum or snapdragon, but they are attached differently. And the seed pods, for me the most interesting bit of the plant, are completely different: they are like minuscule bean pods, but with five bits that surround the seeds. You can see them here, the pointy parts:
When they are ripe and you touch them, they explode! The five bits curl out in a snap! you can hear, when you touch them you get a fright the first time, and the seeds fly away.
They grow often in the shadow of trees, here they are in the open and they are quite numerous (see them in the back to the right? They went on for maybe 50 m more). To this I would add that this has been an unusually wet year, it’s been raining and raining and raining all summer:
They covered quite an area! I have seen them often, but never in such abundance.
Anybody has a clue? Are they native or invasive? They seem not to have a dedicated insect that feeds on them, the leaves are not bitten, nor did I see eggs or cocoons or larvae on them.
Look like impatiens to me
Bang! Solved in one! Perfect, thanks a lot!
It’s Impatiens glandulifera, which is an invasive species wreaking havoc in much of Europe.
ETA: ninjaed.
The overall habit of the plant is different, but the leaf margins, flower shape, and dehiscence of the seedpods reminded me of one of my favorite garden flowers: garden balsam.
And it turns out that this is a wild cousin.
I agree it is beautiful, but the lack of bite marks made me suspect it was invasive. That, and not finding it in any on-line catalogue of local wetlands plants, but that is what the Dope is good at, aren’t you? Well, if it is invasive, it has won. Brandenburg’s lakes and swamps are evidently well suited to its needs and it is thriving.
So I don’t know if you have an iPhone or android (or are one of those weird others 
), but on an iPhone, you go to a picture in Photos, click on it, and swipe up. There is a leaf icon and “Look Up”. Click on it, and it pulls up the answer. I believe Google has the same function.
I tried to use an app called iNaturalist which is supposed to help you identify species, but it did not help. I’ll try your idea on my android (Samsung Galaxy Note 10+, Android 12) but it did not work on a first attempt. Will try again after breakfast.
I have Google Photos on my phone. When I select a picture, there’s a “Google Lens” option. I click that, and press on the screen. A little box appears, and you can pinch or drag it to make it bigger. Google will search for whatever’s in that box.
I saved your first photo, and it worked for me. Good luck! (I just learned about this a few weeks ago - it’s fun.)
Yes, that worked for me too, that is quite impressive, thanks for the explanation!
And not to make iNaturalist look bad: they solved it too, it just took several hours. But two crowd-participants got it right too.
This is what my Picture This app is telling me, also.
It looks very much like what we have in N America Impatiens capensis
A native plant also known as jewelweed or touch me nots. It too pops the seed pods when you touch it.
I don’t know of anyone arguing that I. capensis is invasive in the U.S. (being a native species has a lot to do with that). It’s an enthusiastic self-sower. I have some in the yard; it hasn’t misbehaved.
I. glandulifera a.k.a. policeman’s helmet a.k.a. Himalayan balsam, which is apparently what the OP photographed, is considered invasive in parts of the U.S. though not in others. Some color forms are considered attractive garden plants but I can see it becoming a nuisance.
Also it’s nectar is a favorite for pollinators. Hummingbirds, bees
Oh, I so wish we had hummingbirds in Europe! That is an invasive species I would not mind at all!
I freaked out last year when I thought I saw a hummingbird in the garden here in the UK. It was just a hummingbird moth. Those things are well named!
Wow I never realized that hummingbirds were found only in the Americas. They come to my nectar feeders every day in the summer. Fascinating to watch they are mighty in spirit and fierce in flight.
Birds in the rest of the world are better at remembering the words.
Hummingbirds are beautiful and interesting to watch but tempermentally they are assholes. When I see two of them fighting for access to the 4-station feeder, I just want to yell, “there’s room for both you, you idiots!”