Based on the Samsung Magician info (name, firmware, etc.), you purchased a Samsung 840. This is an early model unit that was later succeeded by the 840 EVO and 840 Pro.
While the 840 EVO and 840 Pro generally can be expected to have sequential write speeds in the 480 MB/s range, the 840 is generally in the 190 MB/s range new.
As to improving it's performance (if running Windows) -
Make sure you have AHCI enabled for that drive.
In Device manager, check the drive's "Policies" to make sure the "Better Performance" box is checked.
In Samsung Magician, under "Performance Optimization", if "Rapid Mode" is available, enable it and if "Trim Status" is available enable it and then click on "Optimize Drive"
That is a lot of write to an early model Samsung (although it probably has a lot left), you may want to consider looking into a newer (less used) drive.