Move in crontab -e editor

I'm trying to manipulate the editor of crontab but it's really really confusing. So I launch the creation of a new crontab with crontab -e Then the default editor opens. Now from there, it's seems to be LAGGING !!?? How do I move around in the editor ? How do I get "--INSERT--" to show and then write my "script" and then type :wq to write and save exit ? How can I go back to writing mode after pushing once esc or : ?