Let’s look at the sentence: "I would definitely go there again. Only when it's not busy." The two parts are related ideas, so it would sound better to connect them with a linking word.
The phrase "Only when it's not busy" shows a condition — you will go again if it's not busy. Some good linking words to show this condition are:
- "if" – means something will happen on the condition that something else is true.
- "provided that" – means the same as "if" but a bit more formal.
- "as long as" – another way to show a condition.
So, the sentence would be better as:
"I would definitely go there again if it’s not busy."
or
"I would definitely go there again provided that it’s not busy."
or
"I would definitely go there again as long as it’s not busy."
Among these, "if" is the most common and simple linking word suitable for a 13-year-old.