Bahçede mangal yaptık.

Bahçe means garden or yard. The ending -de is the locative suffix, which gives the meaning in / at / on depending on context.

So:

• bahçe = garden
• bahçede = in the garden / in the yard

In this sentence, bahçede tells you where the action happened.

In Turkish, mangal yapmak is a very common expression. Literally, it looks like to do/make barbecue, but naturally it means:

• to have a barbecue
• to barbecue
• to grill out

This is one of many Turkish combinations where yapmak is used with a noun to form a natural expression.

So mangal yaptık does not usually mean we built a barbecue grill. In normal conversation, it means we had a barbecue.

Yaptık comes from the verb yapmak = to do / to make.

It breaks down like this:

• yap- = verb stem
• -tı- = past tense
• -k = we

So yaptık means we did / we made.

In this sentence, because of the expression mangal yapmak, it is understood as we had a barbecue.

This happens because of a regular Turkish sound rule.

The past tense suffix is basically -DI, but its form changes depending on the sounds around it:

• d/t changes by consonant harmony
• ı/i/u/ü changes by vowel harmony

Since yap- ends in p, which is a voiceless consonant, the suffix becomes -tı instead of -dı.

So:

• yap + dı would not fit Turkish sound rules here
• yap + tı becomes yaptı
• with -k for we: yaptık

Turkish often leaves out subject pronouns when the verb already shows the person.

Here, -k in yaptık already means we.

So Turkish does not need biz unless you want extra emphasis.

• Bahçede mangal yaptık. = We had a barbecue in the garden.
• Biz bahçede mangal yaptık. = We had a barbecue in the garden.
  (with extra emphasis on we)

Because here mangal is being used in a general, idiomatic way as part of mangal yapmak.

In Turkish, the accusative ending usually appears when the direct object is specific/definite. But in many common expressions with yapmak, the noun stays plain.

So:

• mangal yaptık = we had a barbecue / we barbecued
• mangalı yaptık would suggest a more specific object and could sound like we did the barbecue or even, in another context, we made/built the grill

In this sentence, the plain form mangal is the natural choice.

Turkish word order is flexible, but the most neutral order here is very natural:

• Bahçede mangal yaptık.

That is roughly:

• In the garden, we had a barbecue.

Turkish often puts the verb at the end. The location can come earlier in the sentence quite naturally.

You could change the order for emphasis, but that may change the focus:

• Mangalı bahçede yaptık. = emphasizes in the garden and uses a specific object
• Biz bahçede mangal yaptık. = emphasizes we

So the original sentence sounds normal and neutral.

It can mean either, depending on context.

Mangal can refer to:

• the grill/barbecue equipment
• the barbecue activity or outing

In mangal yapmak, it usually means the activity:

• to have a barbecue
• to barbecue

So in this sentence, people will normally understand it as the event/activity, not the physical grill.

Not exactly. Bahçede mangal yaptık is broader than that. It usually means we had a barbecue as an activity.

If you want to say we cooked meat on the grill, Turkish would more likely use something more specific, such as:

• Bahçede mangalda et pişirdik. = We cooked meat on the grill in the garden.

So:

• mangal yaptık = the barbecue event/activity
• mangalda et pişirdik = the actual cooking on the grill

The Turkish locative suffix -de/-da is broader than any one English preposition. It can correspond to:

• in
• at
• sometimes on

English chooses the most natural preposition based on the noun.

So with bahçe, English usually says:

• in the garden
• in the yard

That is why bahçede becomes in the garden here, even though Turkish is just using its general location suffix.