Check the start and end blocks of /dev/sda1. Then delete the partition /dev/sda1 and create a new partition /dev/sda1 with same start block and extend the size as much required.

Can we extend root partition in Linux?

Resizing a root partition is tricky. In Linux, there isn’t a way to actually resize an existing partition. One should delete the partition and re-create a new partition again with the required size in the same position. … I preferred extending the existing partition to make use of 10GB on the root device.

Can boot partition be extended?

In order to expand the drive you must make sure that there is nothing to the right of the boot partition. then you can right click and extend it.