Removing parts of a sentence connected by “und” and “oder”

Question

Is the following sentence grammatically correct?

So tauschen Sie Tickets oder Reservierungen um und stornieren.

When I start deconstructing the sentence into parts connected with und and oder I get confused. Usually when I remove one part and the conjunction, the remaining sentence is still correct. For instance:

Sie heiratete und bekam ein Kind.

I can deconstruct this to:

Sie 
   heiratete         ← part A
  und                ← conjunction
   bekam ein Kind    ← part B

I can remove heiratete and und or bekam ein Kind and und and the remaining sentence is still correct.

Sie heiratete.
Sie bekam ein Kind.

Applying this logic to the original sentence gets me in trouble.

So 
   tauschen Sie       ← part A (und)
      Tickets         ← part X (oder)
     oder             ← conjunction (oder)
      Reservierungen  ← part Y (oder)
   um                 ← part A (und)
  und                 ← conjunction (und)
   stornieren         ← part B (und)

Clearly, I can remove Tickets and oder or Reservierungen and oder. I can also remove stornieren and und; however, I cannot remove tauschen Sie Tickets oder Reservierungen um and und.

So tauschen Sie Tickets um und stornieren.
So tauschen Sie Reservierungen um und stornieren.
So tauschen Sie Tickets oder Reservierungen um.
So stornieren. [wrong – missing a subject]

Is my thinking flawed?

Answer 1

Removing redundant parts of a sentence after a coordinating conjunction is a common grammatical feature in German (and many other languages). The only things that makes your example weird and even me as a native speaker stumble over it are:

• The second part is very short, while the first part is long. Usually, one would place the shorter part first.

• Stornieren is rarely used without an object.

• Due to its nature, the third person plural as a polite form of address is mostly used in a limited set of sentence structures, to which the sentence in question doesn’t belong.

To illustrate this, let’s approach the sentence in question like this:

1. Sie kauften ein rotes Fahrrad und verkauften ein grünes.

2. Gestern spielten sie Schach und schliefen danach ein.

3. Gestern spielten sie und schliefen.

4. So stornieren Sie und tauschen.

5. So stornieren Sie und tauschen Tickets oder Reservierungen um.

6. So tauschen Sie Tickets oder Reservierungen um und stornieren.

None of the sentences fulfils your criterion and becomes incomplete if you remove the first of the halves joined by und. However, I expect that everybody will agree that the first two sentences are grammatical, and in every subsequent step that increases the weirdness (in my perception), I am doing nothing but swapping words of the same class (3→4), flipping parts of a sentence (5→6), or decreasing complexity (2→3) – neither of which should affect grammaticality.

Answer 2

"So stornieren Sie" is, in a purely grammatical sense, a proper sentence in German. So it is valid, even if it misses an object that you would normally expect.

The sentence as presented does in no way specify what exactly is meant to be canceled, and that could have been a deliberate decision of the writer (Due to the specific ticket system in DB, you can change and cancel train tickets as well as (seat) reservations.)

In order to make this sentence exactly say that, you could reform to

So tauschen und stornieren Sie Tickets und Reservierungen.

which would say the same thing, just a bit more common.

Answer 3

I would have written

So tauschen Sie Tickets um oder stornieren Reservierungen

since Umtausch (exchange) implies a physical thing, whereas Stornierung (Cancellation) is definitely only applicable to immaterial subjects. I consider a ticket as physical and a reservation as immaterial. Given, that today in railway context both may be just cost positions listed in a e-mail, the sloppiness is somewhat excusable, however.