Ich schneide die Bilddatei zu.

Because the verb is zuschneiden, which is a separable verb.

In a normal main clause, German splits this kind of verb into:

• the conjugated stem: schneide
• the prefix: zu

So:

• Ich schneide die Bilddatei zu.

But when the verb is not split, it stays together:

• infinitive: die Bilddatei zuschneiden
• with a modal: Ich will die Bilddatei zuschneiden.
• subordinate clause: ..., weil ich die Bilddatei zuschneide.

So the zu at the end is not a separate word in meaning; it belongs to the verb zuschneiden.

Schneiden means to cut in a general sense.

Zuschneiden usually means something more specific, such as:

• to cut to size
• to trim
• to crop

With Bilddatei, the idea is typically cropping an image file.

So:

• schneiden = cut
• zuschneiden = cut/trim/crop into the desired shape or size

That extra prefix often gives the verb a more goal-oriented meaning.

Because Bilddatei is a feminine noun.

German compound nouns take their gender from the last part of the compound. Here:

• Bild = image, picture
• Datei = file

The last part is Datei, and Datei is feminine: die Datei.

So the whole compound is also feminine:

• die Bilddatei

This is a very useful rule for German compounds.

Because German normally writes compound nouns as one word.

So:

• Bild
  • Datei → Bilddatei

This is completely normal in German. English often uses separate words or hyphens, but German prefers one combined noun.

Other examples:

• Haus
  • Tür → Haustür
• Computer
  • Bildschirm → Computerbildschirm

So Bilddatei is not unusual at all.

It is the accusative case, because it is the direct object of the verb.

The subject is:

• Ich = the person doing the action

The direct object is:

• die Bilddatei = the thing being cropped/cut

So the structure is:

• Ich = subject
• schneide ... zu = verb
• die Bilddatei = direct object in the accusative

A small detail: for feminine singular nouns, the article die is the same in both nominative and accusative. So even though it is accusative here, it still appears as die.

Yes, this is normal German main-clause word order.

The pattern is:

• subject
• conjugated verb
• other sentence elements
• separable prefix at the end

So:

• Ich = subject
• schneide = conjugated verb in second position
• die Bilddatei = object
• zu = separable prefix at the end

This is exactly what you should expect with a separable verb in a main clause.

No. In those situations, zuschneiden usually stays together.

With a modal verb:

• Ich will die Bilddatei zuschneiden.

In a subordinate clause:

• ..., weil ich die Bilddatei zuschneide.

So the split form:

• Ich schneide die Bilddatei zu.

is specifically the normal main-clause pattern.

Yes, schneide is present tense.

It can mean different things depending on context, for example:

• I am cropping the image file.
• I crop the image file.

German present tense often covers both English simple present and present progressive.

So without extra context, the sentence could describe:

• something happening right now
• a regular action
• sometimes even a near-future action

Yes, it is natural.

For digital image editing, German commonly uses ein Bild zuschneiden or eine Bilddatei zuschneiden.

A few notes:

• Bild zuschneiden is often the most everyday way to say crop an image
• Bilddatei zuschneiden is a bit more technical, because it focuses on the file

So the sentence sounds fine, especially in a software or file-editing context.