Merry Christmas To All Forumers

Hi, im having problem with my external drive mentioned above. i accidently remove my USB cable that connects my drive improperly..the next time i plugged in my drive, i couldn't open 1 partition in it..(i made 2 partitions)..an error saying that it is an I/O error when i tried to load on Ubuntu..Last time i had this incident but i managed to load and copied my data from Ubuntu..

My question is,
1-i dont really understand what actually causes the error
2-i've tried chkdsk G:/f, but seems no luck on that..
3-i've also tried disk management utility but it cant open my partition.
4-is there any way i can try to repair the partition?

The other partition is fine and i can access it but t slows down the speed..badly need some help as it contains loads of important data inside..

what i wanna do is just to repair the partition (if it can be repaired), copy my data and format the partition again..need some suggestion and solutions as son as possible..

Thanks guys,