Question About what kind of RAM, brand, and specifications do I need ACER NITRO 5 AN515-52

(A story before the question, sorry lol)
I was curious about my laptop's RAM. I have an ACER NITRO 5 AN515-52, and I've had it for almost 4 years. I use it for games and studies only, with a few downloaded applications for my studies, such as AutoCAD, LTspice, Fluidism, and more. Since I bought it, I haven't paid much attention to the specs. Suddenly, I noticed my laptop becoming slower, especially when starting up Dota 2. During the hero selection stage, my screen doesn't display any heroes, deducting my gold when the match is about to start. When the picked heroes are introduced, my laptop struggles to catch up, leading to delays and hang-ups. Even when exiting the game, there is a noticeable delay. I regularly check and clean the fan, but I don't have thermal paste, and I'm not confident in changing it.

Upon inspecting the RAM, I discovered it is from different brands: Apacer 4GB 2666MHz and Kingston 4GB 2666MHz. This sparked my curiosity, and I came across Kingston's "Fury Beast" SODIMM. I researched it and found features like XMP (Extreme Memory Profile) and other RAM options with different specifications. Initially, I thought I only needed to consider the brand, speed, capacity, number of pins, and DDR type.

(THE QUESTION) Now, my question is, what kind of RAM, brand, and specifications do I need to maximize my laptop's RAM performance, especially for gaming?

Thank you for your patience and your answer.

[Edited the thread to add model name to the title and add issue detail]