The Weak Teacher System

A young man gets a second shot at life after dying in his previous life but there's a catch. Our mc is sent to different anime worlds but the things is he's only as strong as a normal human until he sees a screen appears in front him.
[welcome to the teacher system]
It turns out the system can help others get strong fast but not himself. It turns out if he wants to be safe he has to rely on other people.
So where will he go and who will train he train find out next time on dragon bal- by reading the story