i didn't work coz the partition i want to keep is the second one so i can't use the hand to drag the partition
Format partition one to Mac OS Extended. Then DL the free trial version of Carbon Copy Cloner and use that to clone P2 to P1. Now option key boot and select P1 to boot from. Then use Disk Util to remove P2 and expand P1 to fill the drive.
Lastly go into System Prefs and in Startup Disk set P1 as the boot volume.