Klíče můžeš položit na skříň, ale tašku dej raději na židli.

Because Czech changes noun endings according to case, and different nouns follow different declension patterns.

In this sentence:

• tašku is the direct object of dej
• skříň and židli come after na and show the destination of the movement, so they are also in the accusative

The forms are:

• taška → tašku
  feminine noun, accusative singular ends in -u
• skříň → skříň
  feminine noun, but this pattern has the same form in nominative and accusative singular
• židle → židli
  feminine noun with a different pattern, accusative singular is židli

So they are all behaving normally; they just belong to different noun types.

Because na can take different cases depending on the meaning.

Here it expresses movement to a place / placement onto a surface, so it takes the accusative:

• položit na skříň
• dát na židli

Compare that with location, where na takes the locative:

• Je to na skříni. = It is on the wardrobe/cabinet.
• Je to na židli. = It is on the chair.

A useful shortcut:

• Where to? → usually accusative
• Where? → usually locative

Yes. Na skříň means onto/on top of the wardrobe or cabinet.

If you wanted to say into the wardrobe/cabinet, Czech would use do + genitive:

• do skříně = into the wardrobe/cabinet

So:

• na skříň = on top of it
• do skříně = inside it

The two parts have different tones.

• můžeš položit = you can put
  This sounds like permission or an acceptable option.
• dej = put
  This is an imperative, so it sounds more like an instruction or recommendation.

So the sentence is not just giving two equal options. It suggests:

• the keys can go there,
• but the bag should preferably go on the chair.

That difference is reinforced by raději.

Raději means rather, preferably, or in this kind of sentence often simply better.

So tašku dej raději na židli means something like:

• better put the bag on the chair
• put the bag on the chair instead
• preferably put the bag on the chair

It often softens an imperative and makes it sound more like advice than a blunt command.

Because Czech usually drops subject pronouns when they are already clear from the verb ending.

• můžeš already means you can
• dej is already a you command

So adding ty is usually unnecessary. You would only add it for emphasis or contrast:

• Ty můžeš položit klíče na skříň...
  = You can put the keys on the wardrobe...

That sounds marked, not neutral.

Czech word order is flexible, and it often reflects emphasis and contrast more than basic grammar.

Here, putting Klíče first and then tašku first in the second clause highlights the contrast:

• the keys can go here,
• but the bag should go there.

A more neutral version could be:

• Můžeš položit klíče na skříň, ale tašku dej raději na židli.

That is also correct. The original word order feels a bit more contrastive and natural in context.

Yes. Both can mean put, but they are not exactly identical.

• položit = place / lay down / set down
  Slightly more specific
• dát = very general verb meaning give, but also very commonly put/place

So:

• Klíče můžeš položit na skříň sounds like you can place the keys on the wardrobe
• Tašku dej raději na židli sounds like put the bag on the chair instead

You could also say:

• Tašku polož raději na židli.

That would also be correct. The original sentence simply uses a natural, varied choice of verbs.

Yes. Položit is perfective, which means it presents the action as a single completed act.

That fits this sentence well, because we are talking about one concrete action: putting something somewhere.

If you used an imperfective verb like pokládat, it would usually suggest:

• repeated action,
• habitual action,
• or focus on the process rather than the completed result.

So here položit is the natural choice.

Similarly, dej comes from dát, which is also perfective. An imperfective imperative like dávej would sound wrong here unless you meant something repeated or ongoing.

Yes. It is informal singular, because it uses:

• můžeš
• dej

If you were speaking politely to one person, or to several people, you would use:

• můžete
• dejte

So the sentence would become:

• Klíče můžete položit na skříň, ale tašku dejte raději na židli.

That is the standard formal/plural version.

It is accusative plural.

The base noun is klíč = key. Since it is a masculine inanimate noun, its accusative plural is the same as its nominative plural:

• nominative plural: klíče
• accusative plural: klíče

So even though the form looks like the dictionary plural, in this sentence it is functioning as the object of položit.

A few sounds here are especially important:

• ž as in můžeš, židli
  sounds like the s in measure
• ř as in skříň
  this is a special Czech sound with no exact English equivalent; it is often described as an r mixed with a zh-like quality
• ň as in skříň
  like ny in canyon
• í is a long ee sound
• ů as in můžeš is a long oo sound

So for many learners, the hardest word here is skříň because it combines both ř and ň. That is completely normal.