Acer A315-21-95KF Screen Flickering and Very Slow.

In about January 2018, I bought an Acer Aspire 3.  For the first few months, it was performing perfectly.  After 3-4 months of use, there were some minor issues, like it randomly sleeping when I am working, which I fixed by changing settings to do nothing when lid closed.  Then, after a period of a month, It started getting EXTREMELY slow and the screen started flickering.  I was able to put up with it for a while.  In around June 2019, it got to the level where I couldn't use it for less than 30 seconds without it going into 40 seconds of screen-off time.  I was tired of it, and I bought a MacBook Pro with 128GB storage.  It was smooth sailing for a while, but I ran out of storage.  Then I realized that my Aspire 3 had 1TB that I had used only 200GB of.  It took me a few DAYS to get the computer on, because no matter when I pressed the power button, it didn't work. One day I just randomly tried turning it on and the boot screen showed up and took about 5-10 minutes to get to the lock screen.  The flickering had gone down dramatically, but if I did something "large", like download some security software, or upgrade Microsoft Edge, the CPU fan got really loud and the screen started flickering.  I also want to use this for video editing, because I edit videos for family and memories, and I just like doing it.  I use Windows Movie Maker (From Windows Vista), but I just download it on the computer and just try to use it.  I bought and used some software, like Avira System Speedup Pro, but I got nothing out of it except even MORE available storage and a message that said "Your Computer cannot be optimized further".  I got the exact same response from other services like Norton, and Avast.  I want my computer to speed up. Any Suggestions?