I have increased the root partition with gparted. The operation was successful, the root has the correct size but the problem is with the shrinked partition, file manager shows the old size (the one before resizing) while gparted shows the correct one (after resizing).
I am worried that will overwrite existing data considering it as a free space (the space that is on both partitions). I am not so good with ubuntu (linux in general) and I don't know what to do.
Note. I am using dual boot, Ubnutu 13 and Windows 7 and windows showing me the correct size.