Windows 10: Trouble with laptop

Hi! I am having some problems with my HP 15 Notebook. My first problem is; randomly, a lag will come when I am listening to music or watching a video along with a robotic sound that doesn't match the audio I am listening to. My attempt to fix that that was a Hardware Diagnostics test to see if I could find the problem but there were no problems there, so now I am stumped. My second problem I find hard to explain. It is like when you are using a printer that is running low on ink and some parts of the letter are missing. It only happens on random websites and refreshing may help or it won't. It depends on how my computer is feeling that day. Attached is a picture of that problem. This isn't a huge problem, but I have a few black dots on my screen. I am assuming it is "dead pixels". How can I fix my long list of problems? Any help is appreciated, thank you!

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Best laptop under $800??

Well the last one I suggested seems to be the best for 650$

EDIT: to facilitate your search...

Laptop GFX benchmark list

Laptop CPU Benchmark list

 

Laptop overclocking adventures

hey guys I'm trying to get clockgen to work on my laptop but can't get any of the plls to work, can you please post like exactly what steps I need to take to test each pll to see if it works? my specs are listed to the left
thanks!

 

Laptop with broken screen How much?

I would like suggestions and look in local stores. I dont wanna buy a laptop from someone online. Sorry. But could be a good idea if you asked him about the performance on older games. Gonna make a list ofall laptops people suggest me.

Remove the screen for space purpose here its small desk and if the screen is opened it will hide my 22 inches lcd