Frankly, instead of being concerned about "overprovisioning" your SSD you should be a lot more concerned about correcting that ghastly partition configuration on that drive. How it got that way we don't know and really don't care. But do correct the partition configuration, which will be quite easy.
Delete the 19+ GB, 144+ GB, and 30+ GB partitions so that the resultant unallocated disk-space will be about 214 GB when added to the present 50 GB of disk-space. (Note that you will need to assign drive letters to those three partitions in order to delete them).
So the result will be two partitions - your present C: & D: partitions + about 214 GB of unallocated disk-space. Capiche?
You can do what you want with that unallocated disk-space. Perhaps you could choose to externd the D: partition to encompass all that unallocated disk-space. Whatever.