Can anyone [help me with a solution, ] show me how to use the Past Simple and the Present Perfect in a simple way?
One idea that help some people is retrospection. When we use the present perfect, our feet are firmly in the present, and we are looking back on some situation that began (at least) in the past. We feel some connection with the present itself or with the period of time extending up to the present.
I have worked in China.
I have been to China twice.
I have lived in Prague for ten years.
When we use the Past Simple, we are placing the situation clearly at some past time or in some past period.
I worked in China in 2002.
I went to China in 2002 to work. I went back for a holiday seven years later.
I arrived in Prague in 1998.