I have a Toshiba Satellite L755 laptop. I have got inot a lot of gaming such as ARK :Survival and Wizards 101. They lag a lot, esp the ARK game. Is my laptop able to be upgraded for gaming? Such as RAM, CPU, Graphics etc?
No for graphics, maybe for CPU, likely for RAM. Issue with swapping CPU in laptops is that even if a different one actually fits in the motherboard, that does not mean that the laptop will boot with it. For RAM, easiest thing is to go to www.crucial.com, install and run their scanner, and see what upgrades are available. A bit faster RAM in dual channel may help a bit. Not much though. You won't turn your system into a gaming system, not even close, and any upgrade would likely not get you into playable FPS past low end games.
Generally speaking, you can only upgrade the RAM and hard drive in the vast majority of laptops. Only specific gaming laptop models that generally costs a least $1,400 USD may allow you to upgrade the GPU.
You cannot upgrade the CPU because it is soldered into the motherboard.
If you want better gaming performance, then you really do not have any other choice than to buy a laptop that is more capable of playing games.