it says that you have 44.22GB of Hard Drive space free.
More that enough and is almost certainly not the cause of your slowdown.
RAM is memory, HD is storage.
The more RAM you have, the more programs you can have open at any one time and the machine will run better as it does not have to keep swapping data between the hard drive and the RAM.
With low amounts of RAM, the system uses the hard drive as a temporary storage area for things it wants to keep in memory and as it is slower to move data from RAM to HD, the system slows down.