Soppkniven og soppbørsten ligger i soppkurven.

Because Norwegian usually writes compound nouns as one word.

• sopp = mushroom
• kniv = knife
• børste = brush
• kurv = basket

So:

• soppkniv = mushroom knife
• soppbørste = mushroom brush
• soppkurv = mushroom basket

English often uses spaces in similar expressions, but Norwegian normally does not.

The ending -en marks the definite singular form, which corresponds to English the.

So:

• soppkniv = a mushroom knife

• soppkniven = the mushroom knife

• soppbørste = a mushroom brush

• soppbørsten = the mushroom brush

• soppkurv = a mushroom basket
• soppkurven = the mushroom basket

In this sentence, the speaker is talking about specific items, so the definite forms are used.

Because Norwegian usually puts definiteness on the noun itself instead of using a separate article the way English does.

So English says:

• the basket

But Norwegian often says:

• kurven

The the meaning is built into the ending -en.

The forms you would usually look up are:

• en soppkniv
• en soppbørste
• en soppkurv

Those are the indefinite singular forms, similar to English a mushroom knife, a mushroom brush, and a mushroom basket.

Norwegian often prefers a position/location verb when talking about where a physical object is.

Here, ligger means something like:

• is lying
• is resting
• is located

So ligger i soppkurven sounds natural for objects that are placed inside a basket.

Using er would be understandable in some contexts, but ligger is more idiomatic here. Norwegian often distinguishes:

• ligger = lies / is lying
• står = stands / is standing
• henger = hangs
• sitter = sits

The two nouns form one combined subject:

• Soppkniven og soppbørsten

That whole subject shares the verb ligger.

Also, Norwegian verbs do not change for singular and plural in the present tense. So the same form is used whether the subject is one thing or several.

For example:

• Kniven ligger = The knife is lying
• Knivene ligger = The knives are lying

So ligger works perfectly with both singular and plural subjects.

i means in / inside.

That fits because the knife and brush are inside the basket.

Compare:

• i kurven = in the basket
• på kurven = on the basket

So i is the natural choice here.

Yes. That is a correct sentence too.

It puts more focus on the location:

• Soppkniven og soppbørsten ligger i soppkurven.
• I soppkurven ligger soppkniven og soppbørsten.

When Norwegian moves something else to the front of a main clause, the verb still stays in the second position. That is why ligger comes right after I soppkurven.

The letter ø does not have an exact English equivalent.

A rough guide:

• it is somewhat similar to the vowel in some pronunciations of bird or burn, but with rounded lips
• your lips should be more rounded than for a normal English ur sound

So børste is roughly like BUR-steh, but with a more rounded vowel than English ur.