The simple expresses a completed action. For example,
I've painted the kitchen, and now I'm doing the bathroom.
The continuous expresses an activity over a period of time.
I've got paint in my hair because I've been decorating.
We use the simple if the sentence has a number or quantity, because the simple expresses completion. The continuous isn't possible.
I've been reading all day. I've read ten chapters.
Some verbs have the idea of a long time, for example, wait, work, play, try, learn, rain. These verbs are often found in the continuous. Some verbs don't have the idea of a long time, for example, find, start, buy, die, lose, break, stop. These verbs are more usually found in the simple.
Sometimes there is no difference between the simple and the continuous.
I've played football since I was a boy.
I've been playing football since I was a boy.