Pohyb počítačové myši je rychlý.

Czech normally does not use articles. There is no regular equivalent of English a or the.

So Czech simply says:

• Pohyb počítačové myši je rychlý.

and context tells you whether English should use a, the, or no article at all.

In this sentence, English would most naturally use the because we are probably talking about a specific computer mouse, but Czech does not need to mark that explicitly.

The whole subject is pohyb počítačové myši.

The head noun is pohyb = movement.
The words počítačové myši describe whose movement it is.

So structurally, it is:

• pohyb = movement
• počítačové myši = of the computer mouse
• je rychlý = is fast

Because Czech is using the genitive case here.

The basic dictionary form is:

• počítačová myš

But after a noun like pohyb, Czech expresses movement of something by putting that thing into the genitive:

• počítačová myš → počítačové myši

So:

• pohyb počítačové myši = the movement of the computer mouse

This is a very common Czech pattern: noun + genitive to express of.

Here it is singular: genitive singular of myš.

That can be confusing, because myši can also be a plural form in other contexts. Czech has several forms that look the same.

Here, though, it means:

• of the mouse, not mice

If you wanted of the computer mice, you would normally get:

• počítačových myší

So in this sentence, počítačové myši is understood as singular genitive.

Because adjectives in Czech must agree with the noun they describe in gender, number, and case.

The base form is:

• počítačová myš
  feminine, singular, nominative

But in this sentence, myš becomes genitive singular:

• myši

So the adjective must change too:

• počítačová → počítačové

This is just normal adjective agreement.

Because rychlý is an adjective, while rychle is an adverb.

In this sentence, rychlý describes the noun pohyb:

• Pohyb ... je rychlý.
• The movement ... is fast.

After je, Czech uses an adjective when describing what something is like.

If you used a verb instead, then you would often use the adverb:

• Počítačová myš se pohybuje rychle.
• The computer mouse moves quickly.

So:

• rychlý = fast
• rychle = quickly

Because it agrees with pohyb, which is:

• masculine
• singular
• nominative

Predicate adjectives after je still agree with the subject:

• pohyb → masculine singular
• therefore rychlý

So the sentence is not using some fixed form of fast. The adjective changes to match the noun it describes.

In a normal full sentence, you should use je.

• Pohyb počítačové myši je rychlý.

Czech usually does not drop the present tense of to be in standard sentences. Leaving it out would sound incomplete, poetic, or like a note/headline rather than normal prose.

So for learners, the safe rule is:

• use je in sentences like this

Czech word order is more flexible than English word order, but the given order is the most neutral and natural here:

• Pohyb počítačové myši je rychlý.

You can change word order for emphasis, but then the sentence may sound more marked or stylistically special.

For example:

• Rychlý je pohyb počítačové myši.

This is possible, but it emphasizes rychlý much more.

So the original order is the best default version for a learner.

Yes. Myš can mean both:

• a mouse as an animal
• a computer mouse

Context usually makes the meaning clear. In this sentence, počítačová myš makes it completely clear that we mean the computer device.

Yes, absolutely.

That version is more verb-based:

• Počítačová myš se pohybuje rychle.
• The computer mouse moves quickly.

The original sentence is more noun-based:

• Pohyb počítačové myši je rychlý.
• The movement of the computer mouse is fast.

Both are grammatical and natural. The difference is mainly in style and focus:

• pohyb ... je rychlý focuses on the movement
• myš se pohybuje rychle focuses on the mouse moving