Learn Hardcore German: Ich esse eine Scheibe Käse.

eine Scheibe Käse (a slice of cheese)
eine Tasse Kaffee (a cup of coffee)
ein Glas Wasser (a glass of water) If you mean a slice of a particular cheese, you can add it: eine Scheibe von dem Käse / eine Scheibe vom Käse or the more formal eine Scheibe des Käses.

What case is eine Scheibe, and why is it eine and not ein?

It’s accusative, because it’s the direct object of esse. Scheibe is feminine (die Scheibe), and the accusative feminine article is eine. Compare: masculine would be einen (e.g., Ich esse einen Apfel).

What are the genders of Scheibe and Käse?

die Scheibe (feminine)
der Käse (masculine) In the sentence, the article agrees with Scheibe, not Käse.

Why is there no article before Käse?

After a measure/portion word, the substance is typically article-less: eine Scheibe Käse, eine Scheibe Brot. If you mean a specific cheese you’ve already identified, you can add a definite reference: eine Scheibe des Käses (formal) or eine Scheibe vom Käse (everyday).

How do I pronounce the tricky parts?

Ich: the final ch is the “soft” sound [ç], like the h in “hue” but stronger; not “ish.”
Scheibe: sch = “sh”; ei = “eye”; final e is a quick schwa “uh.” So roughly “SHY-buh.”
Käse: ä is like a long “eh” [eː/ɛː]; the single s is voiced [z]. Roughly “KEH-zuh.”

Does the present esse mean both “I eat” and “I am eating”?

Yes. German present covers both simple and progressive. If you want to stress the progressive, add gerade: Ich esse gerade eine Scheibe Käse.

How is essen conjugated, and is there anything irregular?

Present:

ich esse, du isst, er/sie/es isst, wir essen, ihr esst, sie/Sie essen Note the vowel change in du/er/sie/es. Common past forms:
Perfekt: ich habe … gegessen
Präteritum (more written): ich aß Colloquial speech may drop the final -e: ich ess.

How do I say “two slices of cheese”?

Ich esse zwei Scheiben Käse. Don’t add an -s to Käse. As a compound, you can also say zwei Käsescheiben.

What’s the difference between eine Scheibe Käse, eine Käsescheibe, and ein Stück Käse?

eine Scheibe Käse: a slice (thin, flat) of cheese; neutral, very common.
eine Käsescheibe: a compound noun; often used when talking about slices as a product/type (e.g., packaged slices).
ein Stück Käse: a piece/chunk (shape not necessarily thin/flat).

Can I drop the subject Ich like in Spanish?

No. German normally requires the subject pronoun. Say Ich esse…, not just Esse… (unless you’re asking a question: Esse ich…?).

Can I move parts of the sentence around?

Yes, but keep the finite verb in second position in statements:

Neutral: Ich esse eine Scheibe Käse.
Object fronted for emphasis: Eine Scheibe Käse esse ich.
With an adverb: Heute esse ich eine Scheibe Käse. (Verb still second.)

Why are Scheibe and Käse capitalized?

All nouns are capitalized in German. Verbs and adjectives are not (unless they’re at the start of a sentence or used as nouns).

How would I refer to a specific, known slice?

Use the definite article with the slice: Ich esse die Scheibe Käse. Many speakers prefer the compound in this case: Ich esse die Käsescheibe. If you mean a slice from a specific cheese you’ve mentioned: Ich esse die Scheibe vom Käse or formal … die Scheibe des Käses.

Is Käse countable? When would I say einen Käse?

As food, Käse behaves like a mass noun (no article after measures; plural often unchanged: die Käse for “cheeses” as types). Einen Käse is used for a whole cheese (a cheese wheel/round) or a type: einen Camembert.

How do I say it in the past?

Most commonly the Perfekt: Ich habe eine Scheibe Käse gegessen. Präteritum is also correct but more written/formal: Ich aß eine Scheibe Käse.

Should I use fressen instead of essen?

Use essen for people. Fressen is “to eat” for animals; applying it to people sounds rude or humorous.