I cant change the hertz refresh rate on my samsung

afaik, you can't change laptop display's refresh rate. lcd displays perform optimally at their highest resolution and refresh rate. most laptops have 60 hz as the highest. i have used a few laptops but didn't find any settings to change refresh rates.
look into 'Control Panel\All Control Panel Items\Display\Screen Resolution' and click 'advanced settings'. click 'list all modes' for available display res. and refresh rates.
try changing brightness, contrast ratio, gamma, other settings. make sure your eyes are at the level with the top of the display and you have sufficient ambient light.