I am performing a hdd read surface test with hddscan and it is showing some very slow sectors. Is this ok? Can I fix this somehow?
This is nothing to worry about. Sometimes slow reads are due to small shocks or vibrations to the chassis of the drive, and not something wrong with drive itself.
If you run the test again, I bet you'll get a completely different number of blocks that are slow.
And, as the commenters above me said, the amount of space that is slow is extremely small.