There are many factors that can cause this issue: How large is your hard drive, how large is your RAM, what is the memory load on your hard drive, how many internet programs are you running at one time, what processing speeds have you setup for stuff, and more. I have run a Lenovo with Windows 10 for more than a decade. The videos, images, and music processes use a lot of RAM to hard drive space.
The 1tb harddrive using the 12RAM allows the fastest processing on my W520, but my T60 couldn't handle that internal drive. Check your computer memory, find the system in the menu, right click on your C (full system) drive, check system &/or memory OR use the menu and search MEMORY. With Windows the menu allows you to check all pieces and the system for how much memory you have. Something over 80% full will not function fast.
Videos, sound, images load up processing also. The larger size documents, pictures, videos, and programs pull more memory space. If you have lots of images & videos & documents try adding those to external memory. In addition some external memory devices allow becoming additional hard drive while plugged in.
Hope this helps, here's some normal additional helps: https://www.google.com/search?q=speed+up+my+computer&oq=speed+up+my+&sourceid=silk&ie=UTF-8