i took off the four screws from the bottom , but the tender is tight , it seems like no way to remove the tender
Martinni,
Those four screws are all that holds the tender shell to the underframe. Perhaps you have a little excess paint or glue that seeped into the seams. A little gentle persuasion should release the shell. One of my tenders was a bit sticky when removed for the first time. One thing that might help is running a flat head, jewelers screwdriver around the edge of the seam to see if there is a sticky spot.
To completely separate the two parts, you will have to feed the connector wires/plugs through the slots in the shell, after the screws are removed and the shell is released.
Regards,
Jonathan