1) if you didn't delete the backup Image for W10 then follow the appropriate instructions. Sometimes that's a particular F-Key but your laptop site or manual should state how.
If you can start that it will overwrite W7 with W10 and basically restore you to how it was when you bought it.
2) Otherwise, you can create a W10 install media from another PC:
a) download and run the MS media creation tool
https://www.microsoft.com/en-ca/software-download/windows10
- choose "other PC" option after starting the tool
b) burn to USB stick (or DVD if you have a reader)
c) boot to that (may need to go into BIOS to adjust boot order)
d) choose the SAME version of Windows (probably W10 Home 64-bit)
e) Delete all partitions (except keep the backup partition if it exists. Probably a couple GB's)
f) do NOT enter a key, just skip that.
g) MOST or all drivers should get installed. If something specific is missing, go to the laptop site and find the software section. I doubt any drivers are missing, but there may be some software specific to your laptop.
Other:
I keep hearing about people going with W7 because they think W10 is "spying" on you. That's been blown out of proportion. If the laptop was working fine before the downgrade then your hardware is likely fine.
I'm very happy with Windows 10; I built many computers and none have obvious issues now though I did have a few issues for several months after release in July 29th 2015. I can disable most or all of the spyware if I want, though frankly most of the data collection doesn't bother me in the slightest. For example, I really don't care if they anonymously record how many pictures I looked at. Frankly, many of the articles are click-bait so the worse the title the more viewers they get. Click-bait is getting to be a big problem.
If you keep having issues start with Memtest86 to verify your system memory. www.memtest86.com (run for full pass)