tennai ga sizuka datta node, kanozyo to soko de matiawase wo simasita.

Because 静かだった describes a state, not an action happening at a location.

• 店内が静かだった = the inside of the shop was quiet
• Here, 店内 is the thing being described as quiet, so it takes が

By contrast, で marks the place where an action happens:

• 店内で待ち合わせをしました = I met up inside the shop

So in this sentence:

• 店内が静かだった = the shop interior was quiet
• そこで待ち合わせをしました = we met there

店内 is read てんない.

It means inside the shop/store or the interior of the store.

• 店 = shop/store
• 内 = inside/interior

So 店内が静かだった means that the inside of the store was quiet.

静か is a na-adjective in Japanese. Na-adjectives do not form the past tense like -i adjectives do.

Its forms are:

• 静かだ = is quiet
• 静かです = is quiet (polite)
• 静かだった = was quiet
• 静かでした = was quiet (polite)

So 静かだった simply means was quiet.

ので means because, since, or so. It gives a reason.

In this sentence:

• 店内が静かだったので = because the inside was quiet

Then the main action follows:

• 彼女とそこで待ち合わせをしました = I met up with her there

So the structure is:

• reason + ので + result/action

A natural translation is:

• Because it was quiet inside, I met up with her there.

Both can mean because, but the nuance is a little different.

• ので sounds a bit more neutral, explanatory, and softer
• から can sound more direct or more like the speaker’s own assertion

So:

• 店内が静かだったので、... sounds like a calm explanation
• 店内が静かだったから、... is also correct, but slightly more direct

In many everyday situations, both are possible.

Because the sentence is talking about the situation at that time, in the past.

• 静かなので = because it is quiet
• 静かだったので = because it was quiet

Since the meeting up also happened in the past:

• 待ち合わせをしました = did meet up

it makes sense that the reason is also expressed in the past:

• 店内が静かだったので = because it was quiet inside

彼女 can mean either:

• she / her
• girlfriend

The exact meaning depends on context.

In this sentence, 彼女と just means with her grammatically. Whether that person is simply a female person or the speaker’s girlfriend depends on the larger context.

Here, と means with.

It marks the person the speaker is doing the action together with or the person involved in the meetup.

So:

• 彼女と待ち合わせをしました = I met up with her

This is a very common use of と:

• 友達と話しました = I talked with a friend
• 家族と行きました = I went with my family

No. In this sentence, it is そこ + で, not the conjunction そこで.

Here:

• そこ = there
• で = at/in (marks where the action happens)

So:

• そこで待ち合わせをしました = I met up there

This is different from the conjunction そこで, which means something like:

• so
• therefore
• and so

In this sentence, the meaning is clearly the location phrase there + at.

待ち合わせ means meeting up, rendezvous, or an arranged meeting.

It is often used with する:

• 待ち合わせをする = to meet up / to arrange to meet

So:

• 待ち合わせをしました = met up / had an arranged meeting

It is a polite past form:

• しました = did

So the whole part means:

• 彼女とそこで待ち合わせをしました = I met up with her there

Because 待ち合わせ is being treated as a verbal noun, and をする is the standard pattern.

• 待ち合わせをする = to meet up
• 勉強をする = to study
• 散歩をする = to take a walk

So in this sentence:

• 待ち合わせをしました = did a meetup → more naturally, met up

That is a very common Japanese sentence pattern.

Japanese often puts background information first:

• reason
• condition
• time
• setting

and then gives the main action at the end.

So:

• 店内が静かだったので、 = because it was quiet inside,
• 彼女とそこで待ち合わせをしました。 = I met up with her there.

This word order feels very natural in Japanese.