Wild flowing water - What is correct?

And that is exactly why it is not a natural watercourse. The upper properties each have to ensure that the rainwater stays on their land. From below, one is now obviously starting to defend against the "violation of rights" from above. If everyone has such a dam, then everyone still has to deal with their own water, so to speak, goal achieved.

It is also explained again in the Bavarian Neighborhood Act: "But not only rivers that overflow their banks can cause conflicts in neighborly relations. Courts repeatedly have to deal with cases where water originating on a neighbor’s property causes negative effects on an adjacent property. In this context, lawyers differentiate between so-called eaves water on the one hand and so-called wild flowing water on the other. Eaves water is the water that initially hits a building as rainwater. This water is already not allowed under federal law to be diverted onto neighboring properties, but must be drained on the own property via a sewer connection or, if necessary, also a soakaway pit. In numerous neighbor law and water laws of the states and also in the state building codes there are additional relevant regulations on this. If you want to direct eaves water onto a neighboring property, you depend on the consent of the owner of the neighboring property. Such a process can be legally regulated, for example, by means of a so-called easement. Wild flowing water, in contrast to eaves water, is defined in the Bavarian Water Act as water that originates on a property or naturally accumulates there. Primarily, wild flowing water is the rainwater that directly hits the property (and not a building). According to the provisions of the Bavarian Water Act (comparable regulations exist in other federal states), the wild flowing water is allowed to flow onto the usually lower-lying neighbor's property. However, the owner of the higher property must not alter or intensify the water discharge to the detriment of the lower-lying property owner – for example through excavations, embankments, or reinforcements. Likewise, the lower-lying property owner must not negatively alter the natural inflow of wild flowing water – for example through the construction of a dam – to the detriment of the higher-lying properties. If a property owner does not comply with the above regulations, the negatively affected neighboring property owner generally has a claim for removal and injunction."

With laws, it is always the case that they are built upon each other. So you cannot consider a single law on its own. § 37 is in section 2: Management of surface waters and in § 3 definitions it states in sentence 1: Surface waters the water that flows or stands constantly or temporarily in beds or flows wild from springs; No bed and no spring = no water body. So what comes down through heavy rain and does not infiltrate is not a water body but water, more precisely precipitation water. So, as someone already wrote above. The duty actually lies with the properties above each to prevent drainage downwards.

Ah, then what you want is probably defined by the [Nachbarschaftsgesetz]. But your text is not the legal text, is it? It sounds like it has been editorially revised.

Ah, then what you want is probably defined by the Neighborhood Act. But your text is not the legal text, is it? It sounds like it has been editorially edited.

That was from the Neighbor Rights Guide Bavaria. Actually, I just want to know what is correct. So if it is as you say, then I wonder: the water comes from a field, the farmer will hardly intercept it ... then there are 2 undeveloped properties on which it simply drains onto the first neighbor and from there onto us ... Do undeveloped properties now have to make drainage? The water does not even fall on their property, they only increase the amount .... Unfortunately, I do not understand how it should be done correctly so that no one has a disadvantage / problem.

You, I am not a lawyer either.
What I have found:
WHG § 54 (1) (1) Wastewater is
2. the water that flows off from precipitation collected from areas of built-up or paved surfaces (stormwater).

By definition, it is therefore wastewater. Then further:

§ 55
(2) Stormwater should be infiltrated, dispersed locally or discharged directly or via a sewer system without mixing with wastewater into a body of water, provided that neither water law nor other public law regulations nor water management interests oppose this.

§ 56
Wastewater is to be disposed of by the legal entities under public law who are obligated to do so under state law (wastewater disposal obligors). The states can determine under which conditions wastewater disposal may be assigned to persons other than those named in sentence 1. Those obliged to dispose of wastewater may employ third parties to fulfill their duties.

So Bavarian Water Act (BayWG):
Art. 34
Persons obliged to dispose of wastewater (Regarding § 56 WHG)

(1) Municipalities are obliged to dispose of wastewater, unless otherwise provided in paragraphs 3 and 5. 2This obligation is fulfilled by the municipalities within their own area of responsibility.
(2) By statute, municipalities or special-purpose associations may determine that the acceptance of wastewater may be refused,
1. if the wastewater is better treated by the one at whose premises it arises because of its nature or quantity,
2. if separate treatment of the wastewater due to the settlement structure does not impair the welfare of the general public, or
3. as long as acceptance of the wastewater is not technically or economically feasible due to disproportionate effort.
In the cases of sentence 1 numbers 2 and 3, a wastewater disposal concept is to be drawn up and updated. 3If one of the conditions mentioned in sentence 1 numbers 1 to 3 exists, the district administrative authorities may revokeably exempt other persons obliged to dispose of wastewater from accepting wastewater.
(3) The operators of public transport facilities are responsible for wastewater disposal instead of the municipalities, as far as they are obliged to provide drainage under other regulations and it does not concern wastewater disposal from built properties.
(4) If third parties are permitted to discharge wastewater into a body of water or there is an old right or authorization for this, no regulation under paragraph 2 is required to that extent; the municipal connection and usage obligation remains unaffected.
(5) 1If a municipality or special-purpose association has refused to accept wastewater according to paragraph 2 sentence 1 or if another person obliged to dispose of wastewater has been released from the obligation according to paragraph 2 sentence 3 or paragraph 4, the person authorized to discharge the wastewater into a body of water or at whose premises the wastewater arises shall fulfill this obligation. 2The obligation of the authorized person to discharge takes precedence over the obligation of the person at whose premises the wastewater arises, unless otherwise regulated in a water law permit.
(6) Those obliged under paragraphs 1, 3 and 5 may join together to jointly fulfill the obligation to dispose of wastewater.
(7) Wastewater must be handed over by the one at whose premises it arises to the person obliged to dispose of it under paragraphs 1, 3 and 5.

So maybe take a look at the municipal statute?

Oh man I didn’t think it would be so complicated to find out what the regulations actually are…. Either I’m allowed to build walls then I’ll build one and the person above me will drown or I’m not allowed then the person below has to tear it down again….

Unfortunately you can’t ask our municipality they don’t know themselves…. Maybe I’ll get further at the [Landratsamt]?!

I have to take another close look at the original legal texts.