Ich ändere den Speicherort, damit der Download nicht im falschen Ordner landet.

Because ändern takes a direct object in the accusative case.

• der Speicherort = nominative form
• den Speicherort = accusative form

In this sentence, Ich is the subject, and den Speicherort is the thing being changed:

• Ich = I
• ändere = change
• den Speicherort = the save location / storage location

So the accusative is required.

Speicherort means the place where something is saved. In computer-related German, it often means:

• save location
• storage location
• destination folder

It is a compound noun:

• Speicher = storage / memory
• Ort = place

So literally it is something like storage place.

Damit means so that or in order that. It introduces a clause that expresses purpose.

So:

• Ich ändere den Speicherort = I am changing the save location
• damit der Download nicht im falschen Ordner landet = so that the download does not end up in the wrong folder

This is a very common way in German to express why someone does something.

Because damit is a subordinating conjunction. In German, subordinating conjunctions send the conjugated verb to the end of the clause.

So:

• der Download landet nicht im falschen Ordner = normal main clause word order
• damit der Download nicht im falschen Ordner landet = subordinate clause, so landet moves to the end

This is one of the most important German word-order patterns to learn.

Because der Download is a singular noun.

Even though download might sound like an action in English, in German der Download is treated as a masculine singular noun. Therefore the verb must also be singular:

• der Download landet = the download ends up
• die Downloads landen = the downloads end up

So landet agrees with the singular subject der Download.

Literally, yes, landen means to land. But in everyday German it is also used figuratively to mean:

• to end up
• to wind up
• to arrive in a place, often unintentionally

So here:

• im falschen Ordner landet = ends up in the wrong folder

This figurative use is very common in both spoken and written German.

Im is a contraction of in dem:

• in dem → im

The noun Ordner is masculine (der Ordner), and after in with a location, German uses the dative case:

• der Ordner → dem Ordner
• in dem Ordner → im Ordner

The adjective must also match the dative masculine form:

• im falschen Ordner = in the wrong folder

In German, nicht usually comes before the part of the sentence being negated.

Here the idea is not that the download does not exist; the idea is that it should not end up in the wrong folder. So nicht appears before the location phrase:

• nicht im falschen Ordner landen = not end up in the wrong folder

Compare:

• Der Download landet nicht im falschen Ordner. = The download does not end up in the wrong folder.
• Der Download landet im richtigen Ordner. = The download ends up in the correct folder.

They are related, but not identical.

• Speicherort = the save/storage location in a broader sense
• Ordner = folder

A Speicherort might be a specific folder, drive, or destination chosen in a program. An Ordner is specifically a folder.

So in this sentence:

• You change the Speicherort,
• so the download does not end up in the wrong Ordner.

Because in German, all nouns are capitalized.

So:

• der Download
• der Speicherort
• der Ordner

This is true whether the noun is native German or borrowed from English.

Not naturally in this sentence, because um...zu is usually used when the subject of both clauses is the same.

For example:

• Ich ändere den Speicherort, um Platz zu sparen.
  • I change the save location in order to save space.

Here, the subject is Ich in both ideas.

But in your sentence, the second clause has its own subject:

• der Download

So damit is the correct choice:

• Ich ändere den Speicherort, damit der Download nicht im falschen Ordner landet.

Yes. German present tense often covers both:

• I change
• I am changing

So Ich ändere den Speicherort can mean either, depending on context.

German does have ways to emphasize an ongoing action, but usually the simple present is enough.

Yes, it sounds natural and idiomatic, especially in a technical or everyday computer context.

It clearly expresses:

1. the action: Ich ändere den Speicherort
2. the purpose: damit der Download nicht im falschen Ordner landet

A native speaker would understand it immediately.