Learn Hardcore Japanese: ninki no mise no mae ni gyouretu ga dekite ita node, betu no mise ni ikimasita. - Because there was a line in front of the popular shop, I went to a different shop.

Breakdown of ninki no mise no mae ni gyouretsu ga dekite ita node, betsu no mise ni ikimashita.

What does 人気の店 mean? Is 人気 an adjective here?

人気 is a noun that means popularity or being popular.

So:

In Japanese, a noun can modify another noun with の, so 人気の店 is a very natural way to say a popular shop.

A related expression is:

Both are natural, but 人気の店 is more compact.

Why are there two の in 人気の店の前?

Each の links one noun to the next.

Break it down like this:

Put them together:

So the structure is:

This kind of noun chaining is very common in Japanese.

What does 前 mean here? Could 前に mean in time?