Learn English – say “I have been dedicated the work”

You need the present perfect continuous to place emphasis on the duration of the activity and the fact that it has continued into the present (your arrival). So, correct is:

How long have you been waiting for me?

A common, and shorter, way to ask the same question is:

Have you been waiting long?

It's been a long time since I went to Canada.

To me, the above sentence is ideal only in cases where there is only one visit to Canada. In that sense, it would be both a first and the last (most recent) visit. That said, it's a valid construction in a situation where multiple visits had occurred, but in these cases I’d argue for:

It's been a long time since I have been to Canada.

The way I figure it, the statement above has two main pieces of information:

1. I have been to Canada (at least once; possibly multiple times)

2. It has been a long time since then (since my last visit)

Broken down the same way, the first sentence has these two main pieces of information:

1. I went to Canada (most likely just once)
2. It's been a long time since then (since my one and only visit)

So it comes down to what you want to say. This might be the situation:

1. I went to Canada throughout my teens
2. It's been a long time since then

You could make an argument for either option in this case, but I maintain that the second sentence would more clearly indicate multiple visits.