Es regnet, trotzdem machen wir einen kurzen Spaziergang im Park.

With weather verbs like regnen, German normally uses a formal or dummy subject: es.

It does not refer to a real thing. It is just there because German sentences usually need a subject.

So:

• Es regnet = It’s raining
• Es schneit = It’s snowing

English does the same thing with it.

German Präsens often covers both meanings.

So Es regnet can mean:

• it rains
• it’s raining

In this sentence, the context clearly makes it mean it’s raining right now.

The same is true for machen wir:

• literally present tense
• in English, often best translated as we’re taking / we are going for

Trotzdem means nevertheless, nonetheless, even so, or despite that.

It connects the two ideas like this:

• Es regnet = one fact
• trotzdem machen wir... = in spite of that fact, we still do it

So it marks a strong contrast.

Because trotzdem is not a subordinating conjunction like weil or obwohl.

It is a connecting adverb, and the clause after it is still a main clause. In a German main clause, the finite verb must be in second position.

Here:

• position 1: trotzdem
• position 2: machen
• then: wir

So:

• trotzdem machen wir... ✓
• trotzdem wir machen... ✗

No, not quite.

• aber is a coordinating conjunction
  
  • Es regnet, aber wir machen einen Spaziergang.
• trotzdem is a conjunctive adverb
  
  • Es regnet, trotzdem machen wir einen Spaziergang.

The meaning is similar, but the grammar is different.

A useful shortcut:

• aber behaves more like but
• trotzdem behaves more like nevertheless / even so

Because the sentence contains two separate main clauses:

1. Es regnet
2. trotzdem machen wir einen kurzen Spaziergang im Park

The comma separates those two clauses in writing.

Einen Spaziergang machen is a common German expression meaning to take a walk or to go for a walk.

German often uses machen in fixed expressions like this.

You could also say:

• Wir gehen im Park spazieren.

That means roughly the same thing:

• einen Spaziergang machen = take a walk
• spazieren gehen = go walking / go for a walk

Both are natural.

Because Spaziergang is the direct object of machen, so it is in the accusative case.

• dictionary form: der Spaziergang (masculine)
• masculine accusative with ein becomes einen

So:

• nominative: ein kurzer Spaziergang
• accusative: einen kurzen Spaziergang

That is also why the adjective becomes kurzen.

The adjective ending changes because it has to match:

• the case: accusative
• the gender: masculine
• the article pattern: einen

So in einen kurzen Spaziergang:

• einen shows masculine accusative
• the adjective takes the ending -en

Compare:

• ein kurzer Spaziergang = nominative
• einen kurzen Spaziergang = accusative

Because im means in dem, which is dative.

With in, German makes a very common distinction:

• location → dative
• direction toward a destination → accusative

So:

• im Park = in the park / located in the park
• in den Park = into the park

Here the park is the place where the walk happens, so im Park is the natural form.

Yes, absolutely. That is very natural too.

The difference is grammatical:

• trotzdem introduces a new main clause
  
  • Es regnet, trotzdem machen wir...
• obwohl introduces a subordinate clause
  
  • Obwohl es regnet, machen wir...

With obwohl, the verb goes to the end of the subordinate clause:

• obwohl es regnet

The meanings are very close:

• trotzdem = nevertheless / despite that
• obwohl = although / even though

Yes.

For example:

• Es regnet, trotzdem machen wir einen kurzen Spaziergang im Park.
• Es regnet. Wir machen trotzdem einen kurzen Spaziergang im Park.

Both are possible.

The difference is mainly emphasis:

• putting trotzdem first makes the contrast especially clear
• putting it later sounds more like we still go for a short walk

So the meaning stays similar, but the focus shifts a little.