How to upgrade from Sierra 10.12.6 to High Sierra 10.13

Having terrible issue with intermittent wifi/internet connection that Genius Bar cannot figure out, so they suspect possibly related to something with my main "user account" and said to try to create new one and if doesn't work, then recommended to backup, restore clean and upgrade to High Sierra from Sierra. Tried downloading High Sierra from App Store, but says is version 10.13.6, which I downloaded and attempted install. It goes through the install prompts then error pops up and says try again. Try again and again...no change. 52GB free so that's not an issues. First Aid check good too. Is it because not 10.13? I cannot locate 10.13...only 10.13.6.

FYI regarding internet issues - have scoured the net and forums about this issue. Spoke to Apple Support, spent hour+ at Genius Bar. Tried EVERYTHING suggested to no avail. Scoured and tried everything on YT videos to "speed up" or "clean" my computer, no avail. Tried changing a bunch of network settings, no change. The crazy thing is the genius diagnostic says wifi and ethernet, etc is good. Doesn't even work with direct ethernet connection. Doesn't work at all on my main user account and only intermittent on other accounts created. Will work for a short time on them and then drops. Only sometimes will it reconnect after a restart...bizarre. Note: posting this on 3rd new user created today, and still connected to wifi so far...

Ran a DriveDX check on it and says good and hard drive at 86.8% overall health with zero issues. Mid 2012 Mac Book Pro 13", Processor 2.5 GHz Intel Core i5, Memory 4 GB 1600 MHz DDR3, Graphics Intel HD Graphics 4000 1536 MB. Gently used, works great otherwise. I know High Sierra is last update I can do. Pretty nervous it will jack up my Adobe Creative Suite 6 usability, but at this point, I need it for more important work than I use CS6 for.

Losing my mind! Only found one other person on a forum somewhere had exact same issue. Tried everything suggested to him and like him, had no change...

Praying to the tech angels for some illumination! Thanks for reading and pondering!