Τα αθλητικά μου είναι παλιά, και μάλλον πρέπει να βρω άλλο νούμερο πριν αρχίσω να περπατάω περισσότερο.

In everyday Greek, τα αθλητικά is a very common shortened way to say τα αθλητικά παπούτσια — literally the athletic shoes.

So the noun παπούτσια is left out because it is understood from context. This is very natural in Greek.

• αθλητικός = athletic, sports-related
• τα αθλητικά = sports shoes, trainers, sneakers

This is one of those cases where an adjective is being used like a noun.

Because it refers to a pair of shoes, and in Greek shoes are normally spoken of in the plural, just as in English we often say my shoes are old, not my shoe is old.

So:

• το αθλητικό = one athletic shoe
• τα αθλητικά = athletic shoes / trainers

That is why the rest of the sentence also agrees with a neuter plural noun.

Greek possessive words like μου, σου, του, της, μας are usually placed after the noun.

So:

• τα αθλητικά μου = my trainers
• literally: the trainers my

This is completely normal Greek word order. English puts the possessive before the noun, but Greek usually puts these short possessive forms after it.

Because παλιά agrees with τα αθλητικά, which is neuter plural.

Here is the pattern:

• παλιός = masculine singular
• παλιά = feminine singular or neuter plural
• παλιό = neuter singular

Since αθλητικά is neuter plural, the adjective must also be neuter plural:

• Τα αθλητικά μου είναι παλιά = My trainers are old

It can suggest either, depending on context, and in this sentence it strongly feels like old / worn / no longer suitable.

Because the speaker then says they probably need to find another size, the idea is not just age in a historical sense, but that the shoes are no longer right for them.

So παλιά here is best understood as something like:

• old
• worn
• outdated
• not good anymore

Here μάλλον means probably, most likely, or I guess.

So:

• μάλλον πρέπει να βρω... = I probably need to find...

It softens the statement a little. The speaker is not making a very hard, absolute statement; they are saying this is likely the right conclusion.

Be careful: μάλλον can sometimes also mean rather in other contexts, but here probably is the natural meaning.

After πρέπει (it is necessary / I have to / should), Greek normally uses να + subjunctive.

So:

• πρέπει να βρω = I need to find / I should find

You cannot normally say πρέπει βρίσκω here.

Also, βρω is the aorist subjunctive form of βρίσκω. In this sentence, that makes sense because the speaker means find one new size as a single complete action, not be finding / keep looking in an ongoing way.

Compare:

• πρέπει να βρω = I need to find
• πρέπει να βρίσκω = I need to be finding / keep finding
  This would not fit well here.

This is about aspect, which is very important in Greek.

• βρω = aorist subjunctive, focusing on a single complete action
• βρίσκω / να βρίσκω = imperfective, focusing on process, repetition, or duration

In this sentence, the speaker wants to find another size once. That is a complete, goal-oriented action, so βρω is the natural choice.

So πρέπει να βρω άλλο νούμερο means:

• I need to find another size

not:

• I need to be finding another size repeatedly

Here νούμερο means size, especially for shoes or clothes.

So:

• άλλο νούμερο = another size / a different size

Literally, νούμερο means number, but in shopping contexts Greek often uses it the same way English uses size.

Examples:

• Τι νούμερο φοράς; = What size do you wear?
• Θέλω μεγαλύτερο νούμερο. = I want a bigger size.

Because νούμερο is a neuter singular noun.

The adjective άλλος must agree with the noun:

• άλλος = masculine singular
• άλλη = feminine singular
• άλλο = neuter singular

Since νούμερο is neuter singular, Greek uses άλλο νούμερο.

πριν means before. When it refers to something that has not happened yet, Greek commonly uses a verb in the subjunctive.

So:

• πριν αρχίσω = before I start

Here αρχίσω is the aorist subjunctive of αρχίζω.

This is natural because the action of starting has not happened yet; it is something the speaker is talking about in advance.

After πριν, Greek often uses the subjunctive form without an extra να in modern everyday usage.

So:

• πριν αρχίσω = before I start

That is the standard pattern here.

Also, αρχίσω is used instead of αρχίζω because the speaker means the moment of starting as a complete event, not an ongoing process.

So the idea is:

• before I begin...

not:

• before I am beginning...

Again, this is about aspect.

• να περπατάω = to walk, to be walking, to walk regularly / for a period of time
• να περπατήσω = to walk once, or to complete a walking action

In this sentence, the meaning is start walking more in the sense of doing more walking in general / more often / for longer. That is ongoing or habitual, so Greek uses the imperfective form:

• να περπατάω περισσότερο

If the speaker meant one single walk, the aorist might make more sense, but that is not the idea here.

Here περισσότερο is an adverb meaning more.

It modifies περπατάω:

• να περπατάω περισσότερο = to walk more

It does not mean more big or anything like that here. It simply increases the amount or frequency of the action.

You can think of it as:

• walk more
• do more walking

Yes. They are two common forms of the same verb:

• περπατάω
• περπατώ

Both mean I walk.

In modern spoken Greek, forms in -άω are very common and natural. So να περπατάω is completely standard.

You may also hear:

• να περπατώ

Both are correct; the choice is often about style, register, or personal preference.

A helpful way to break it up is:

• Τα αθλητικά μου είναι παλιά = My trainers are old
• και μάλλον πρέπει να βρω άλλο νούμερο = and I probably need to find another size
• πριν αρχίσω να περπατάω περισσότερο = before I start walking more

So the sentence moves like this:

1. state the problem
2. state the likely solution
3. explain why that matters now

That makes the Greek sentence easier to process as three logical parts rather than one long string of words.