Kukuřice je v alobalu vedle žampionu.

Yes, kukuřice is singular here. It is a feminine singular noun meaning corn or maize. In this sentence, the verb je also shows that the subject is singular, because je means is.

The ending -e does not automatically mean plural in Czech.

Je is the 3rd person singular present form of být, which means to be.

So:

• já jsem = I am
• ty jsi = you are
• on/ona/ono je = he/she/it is

Here, Kukuřice je... = The corn is...

Because the preposition v means in and, when it shows location, it requires the locative case.

The basic form is:

• alobal = foil / aluminum foil

After v, it changes to:

• v alobalu = in foil

So this is a case change caused by the preposition.

Alobal is the normal Czech word for aluminum foil or tin foil.

So v alobalu often means not only in the foil, but very naturally wrapped in foil.

Because vedle means next to / beside, and it requires the genitive case.

The base form is:

• žampion = champignon / button mushroom

After vedle, it becomes:

• vedle žampionu = next to the mushroom

So here the noun changes because of the preposition vedle.

Žampion usually means a button mushroom or champignon, the common cultivated mushroom used in cooking.

It is more specific than the very general English word mushroom.

Because Czech does not have articles like English.

So kukuřice can mean:

• corn
• the corn
• a corn

depending on context, although in natural English you would usually say the corn here.

The same applies to žampionu:

• next to the mushroom
• next to a mushroom

Context tells you which is meant.

No. Czech word order is fairly flexible.

Kukuřice je v alobalu vedle žampionu is a normal, neutral way to say it. But Czech can move parts around for emphasis, for example:

• Vedle žampionu je kukuřice v alobalu.
• V alobalu je kukuřice vedle žampionu.

These versions still mean roughly the same thing, but the emphasis changes.

It can mean both, depending on context.

Literally, v alobalu is in foil. But in real usage, Czech often uses this phrase where English would say wrapped in foil.

So if this is about food, Kukuřice je v alobalu very naturally suggests The corn is wrapped in foil.

A rough English approximation is:

• kukuřice ≈ koo-koo-rzhi-tseh

The hardest sound is ř, which is a special Czech sound. It is something like an r and zh sound produced together. Learners usually need time to master it, so do not worry if it feels difficult at first.

Yes:

• v + locative → v alobalu
• vedle + genitive → vedle žampionu

That is one of the key things this sentence teaches: Czech prepositions often require a specific case, and the noun changes form because of that.