रैकेट पर पकड़ मज़बूत रखिए।

Here पकड़ is a noun, meaning grip or hold.

So the sentence is built like:

• रैकेट पर = on the racket
• पकड़ = grip
• मज़बूत = strong/firm
• रखिए = keep

A very literal translation would be:

Keep the grip on the racket firm.

This is related to the verb पकड़ना (to hold / to catch), but in this sentence पकड़ is not a verb.

Hindi often expresses this idea with X पर पकड़ = grip on X.

So:

• रैकेट पर पकड़ = grip on the racket
• रस्सी पर पकड़ = grip on the rope

This is a very natural Hindi structure. English might prefer your grip on the racket, but Hindi does not need to say your unless it is important for emphasis.

पर usually means on, and here it marks the object that the grip is on.

So:

• रैकेट पर = on the racket
• पकड़ रैकेट पर = grip on the racket

In English, on also works well: a firm grip on the racket.

रखिए is a polite imperative form of रखना, which usually means to keep or to place.

In this sentence, it means keep in the sense of maintain:

• मज़बूत रखिए = keep it firm
• साफ़ रखिए = keep it clean
• सीधा रखिए = keep it straight

So the sentence is not telling you to physically put something somewhere. It is telling you to maintain a firm grip.

Because रखिए is a polite or respectful command.

Compare:

• रखो = keep (informal)
• रखिए = keep (polite)
• रखना = to keep (infinitive, not a command)

In instructions from a coach, teacher, or formal guide, रखिए sounds natural and polite.

Yes, they are the same in meaning and pronunciation for most learners.

• रखिए is the more standard modern spelling.
• रखिये is also commonly seen.

Both mean please keep / keep politely.

Hindi often uses the pattern:

noun + adjective + रखना

So instead of saying hold firmly, Hindi may say keep the grip firm.

That is why:

• पकड़ मज़बूत रखिए = keep the grip firm

A more verb-focused alternative is also possible, such as:

• रैकेट को मज़बूती से पकड़िए। = Hold the racket firmly.

Both are natural, but the original sentence focuses on the grip itself.

No, मज़बूत stays the same.

Many Hindi adjectives do not change form for gender or number. मज़बूत is one of them.

Since पकड़ is feminine, some learners expect a feminine ending, but मज़बूत does not change:

• मज़बूत पकड़ = firm grip
• मज़बूत हाथ = strong hand
• मज़बूत दीवार = strong wall

Yes, it is normal.

The order is:

• रैकेट पर = on the racket
• पकड़ = grip
• मज़बूत = firm
• रखिए = keep

Hindi often places the main verb at the end. So a literal order is:

On the racket, grip firm keep.

That sounds strange in English, but it is normal in Hindi.

Hindi often leaves out possessive words like your when they are obvious from context.

So:

• रैकेट पर पकड़ मज़बूत रखिए।

naturally means:

• Keep your grip on the racket firm.

If needed, Hindi could make it more explicit, but it usually does not have to.

It is a borrowed word, ultimately from English racket, written in Devanagari as रैकेट.

Hindi uses many borrowed words for sports equipment, especially in modern speech. So this is completely normal.

Yes, that is a very natural alternative.

• रैकेट पर पकड़ मज़बूत रखिए। = Keep a firm grip on the racket.
• रैकेट को मज़बूती से पकड़िए। = Hold the racket firmly.

The difference is mostly one of focus:

• पकड़ मज़बूत रखिए focuses on the grip
• मज़बूती से पकड़िए focuses on the action of holding

In practical meaning, they are very close.