Dede torunuyla parkta yürüyor.

A useful breakdown is:

• dede = grandfather / grandpa
• torunuyla = with his/her grandchild
• parkta = in/at the park
• yürüyor = is walking

So the sentence structure is basically:

• Subject: dede
• Companion phrase: torunuyla
• Place: parkta
• Verb: yürüyor

Because Turkish usually puts the main verb last.

That is one of the most noticeable differences from English. In English, you would normally say Grandfather is walking... with the verb near the beginning. In Turkish, it is very common to place other information first and finish with the verb.

So:

• Dede torunuyla parkta yürüyor.

feels very natural in Turkish.

Yürüyor is the present continuous form.

It comes from:

• yürü- = to walk
• -yor = present continuous marker

So yürüyor means is walking.

In context, this tense can sometimes also cover meanings that English might express a little differently, but the basic idea here is an action that is currently in progress.

Turkish often does not use subject pronouns unless they are needed for emphasis or clarity.

Here, the subject is already given as dede, so there is no need to add a separate word for he.

Also, Turkish commonly allows the subject to be understood from context. Even a sentence like Yürüyor can mean He/She/It is walking, depending on context.

Parkta is:

• park = park
• -ta = locative ending, meaning in / at / on

So parkta means in the park or at the park.

The locative suffix has different forms: -da, -de, -ta, -te.

Here it becomes -ta because:

1. the last vowel in park is a, so the suffix uses a
2. the word ends in k, which is a voiceless consonant, so d changes to t

That is why it is parkta, not parkda.

Because the meaning with is often attached directly to the noun in Turkish.

Here:

• torunu = his/her grandchild
• ile = with

These combine into:

• torunu + ile → torunuyla

When ile is attached, it usually appears as -la / -le, and after a vowel a buffer y is inserted.

So torunuyla is the normal combined form of torunu ile.

Because torunuyla does not just mean with a grandchild. It specifically includes a possessive idea:

• torun = grandchild
• torunu = his/her grandchild
• torunuyla = with his/her grandchild

In this sentence, that naturally refers back to dede.

So torunuyla is closer to with his grandchild than to a more general with a grandchild.

It can mean either.

Torun is gender-neutral and means grandchild. Turkish very often does not mark gender in nouns the way English sometimes does.

So from the word torun alone, you cannot tell whether the child is male or female.

Because Turkish does not use articles the same way English does.

English usually needs words like the and a/an, but Turkish often leaves that information to context.

So:

• dede can mean the grandfather or just grandfather/grandpa, depending on context
• parkta can mean in the park
• torunuyla can mean with his/her grandchild

Turkish does have bir, which can work like a/an in some situations, but it is not used the same way English uses articles.

Yes.

You can say:

• Dede torunu ile parkta yürüyor.

This means the same thing as:

• Dede torunuyla parkta yürüyor.

The attached form is very common in everyday Turkish, and often sounds more natural and compact.

Yes, Turkish word order is fairly flexible.

For example, these are possible:

• Dede torunuyla parkta yürüyor.
• Dede parkta torunuyla yürüyor.
• Parkta dede torunuyla yürüyor.

They all keep roughly the same core meaning, but the focus may shift slightly depending on which part comes earlier.

The most important thing is that the verb usually stays at the end.

It can be either, depending on context and tone.

• dede is the normal word for grandfather
• in many contexts, it can also feel like grandpa

So whether you translate it more formally or more warmly depends on the situation, not just the word by itself.