I have a pretty expensive gaming laptop that I got for highschool graduation in 2015. It's held up and been very reliable since I got it, but after a while it became slow when doing anything other than gaming. Opening any kind of apps, windows, or even file explorer takes way longer than it should. I factory reset/wiped the computer a few months back to see if it would help, and while it improved performance a little bit, it didn't help much. Apps also often crash. Any browser I use, even Chrome, freezes for a bit when I first open it. And if left alone for long enough it becomes unresponsive and crashes, and won't open again unless I force crash it in task manager. However, once I get into a game, I don't have any problems while gaming. FPS are usually 70-90+ depending on the game, and I don't have any crashing problems with it.
Computer model: Lenovo Y700 ideapad touch Gaming Laptop
Processor: Intel Core i7
x64 bit, Windows 10
8GB Ram
1TB Storage
GPU: GeForce GTX 960M
And it came with Nvidia GeForce installed.
What I've tried: I asked for help directly from where I bought it, but they weren't much help at all. After resetting, I also had someone from Windows Support take remote control of my computer to fix and edit some things. This helped for about a day, but it went right back to being slow again. I don't have the money to buy a new one, and I won't for a while. Is there some way to improve this laptops performance?
Added (1). I still have over half of my computers memory free to use, and almost never have more than 2 or 3 things open and running at a time. The computer also takes way longer to start up after being shut off or restarted than it should. When it does finally come back on and go to the desktop, it takes a good 5 minutes for any of my applications to start showing up on screen, including my taskbar at the bottom.
Added (2). I don't have many programs set to boot on startup. The only ones I currently have enabled are Steam, Discord and McAfee.