As Dan has already pointed out, your screen is cracked which has broken the electrical circuits for part of the screen. That sort of damage cannot be repaired; the only solution is to replace the screen.
iFixit has a guide showing how to replace the complete display assembly, which would fix the problem with your screen.
[guide|168188|Acer Aspire 3 A315-24P-R7VH Display Assembly Replacement - iFixit Repair Guide]
Be aware that it is probably possible to replace just the LCD itself rather than the entire display assembly, but we don't have a guide for that repair here on iFixit. I did locate a YouTube video detailing the procedure and I must say it's certainly easier than replacing the complete assembly. Basically you just pry off the bezel then there's like four screws holding the LCD in place. Chances are it will be cheaper too, since you're buying just the LCD and not the whole display.
[link|https://www.youtube.com/watch?v=ci9rm9fiQHg|How to replace LCD for Acer Aspire 3 A315 series - YouTube]
From past experience the best method I've found for locating a replacement part is to go ahead and open up the display as shown in the video, then take down the manufacturer and model number of the LCD itself. Laptop makers rarely make their own screens; they're usually off-the-shelf parts that may be used in several different computers. So you may end up searching using the model number of your computer and/or the model number of the LCD and possibly even other models of computers that use that same screen if you find any. I've used this method successfully when I had to find an LCD for a Compaq Chromebook; the same screen was used on a Dell laptop that I found cheaply.
Good luck, hope this information gives you what you need to know.