|You can partition the drive using as many partitions as you have free drive letters. |
If you intend to use the external drive as the sole receptacle of your personal files i would urge you to reconsider.
You should always maintain at least TWO copies of any data you wish to keep.
All hard drives are subject to failure at any time. Mechanical failure is not the only risk. Electrical surges can render the drive unreadable as can viruses, improper removal and a host of other possibilities. Those drives are intended to be used as a transport and/or backup medium.