How to merge ext4 partition containing data with unallocated partition?

I’m installing Windows to update my BIOS. I’ve removed a previous partition but I can’t merge free partition to my original partition. How to solve this problem? I don’t want to format the ext4 partition.

The best solution would be using gparted live CD.

Boot up with this Live disk, and follow the instructions to extend the partition.

See also Features.