My resident visa cancel after 20 days over stay...

If you exceed the validity period of the visa or residence permit, you will be obliged to pay a fine of one hundred dirhams for the missing day of residence in violation.
You can reduce the fine if you are leaving the UAE, and you can request a 50% reduction in exchange for a ban from entering the UAE for a year. If you want to modify your residency status by converting the visa from a visit visa to work visa, in that case you must pay the full fine, and it will not be reduced. Also, the public administration of residence is the entity to which you can apply for a reduction of the residence fine if there is justification for that.

You must visit the General Administration of Residence to follow up on the request to reduce the fine