How to resize HD-89 built-in storage in favor of data partition?

Question

Android

There is a tablet on MTK8389. A section of only 1 GB is allocated under data - programs, of course, do not fit already. The rest of the memory is allocated for the built-in "sd card". How to remove or reduce a flash drive partition in favor of a data partition? Root is. But apart from fdisk, there is nothing in the console. delete a partition or repartition without okorpichiv I do not know how. there is no cwm for it.