Windows [SOLVED]game is running WAY too slow, unplayable for a year

[ceviche]

hi, im new here! i made this account bc i want to help my friend who's having this terrible issue with his game, but is really busy to post a thread on his own at the moment! he loves playing stardew during his free time and has been trying to solve this for about a year now with no success.
he plays on steam and his game is unmodded. his pc has 8gb RAM and i5 cpu, the game used to run just fine until one day it didn't.

he wrote me a list of issues:
- game takes too long to launch after hitting play on steam;
- lags on menu and character creation;
- when opening his saved games menu, the game window stops responding for a few minutes;
- after finally opening a save file, the game takes around 30 minutes to load (it stays in the black "[Loading...]" screen for 30 mins);
- when playing, he deals with a lot of stuttering too: just walking around the map causes the game to suddenly freeze while still running somehow, so he loses around 20-60 in-game minutes bc of that and he never has enough time to do what he normally could in a full in-game day. it lags when watering plants, fishing, mining (so basically everything). he says it's impossible to mine and fish since these tasks need quick action;
- when entering/leaving indoors or going from one area of the map to another, the game freezes in the loading screen and takes a good while to load.

he tried a lot of suggested solutions he saw on reddit and this forum, which i'll list below bc unfortunately none worked:
- resetting his pc;
- doing a fresh download of stardew valley;
- deleted startup preferences;
- updated his gpu drivers;
- played 100% vanilla;
- launched with smapi but no mods;
- launched with smapi with 2 mods;
- set compatibility mode to windows 8;
- set steam compatibility mode to 32bits (this one did ease the loading time a little bit, but it doesn't let him play with mods or friends so he basically can't do the stuff he's most interested in);
- updated XNA;
- checked task manager for cpu and gpu usage (the %s are totally okay, not even near 100% of anything. the game was supposed to run fine);
- set high priority for stardew valley;
- tried the windows troubleshooter;
- tried to play both windowed and full screen;
- he also tried all of the above with no interference of an antivirus.

please help!!

 

[ceviche]

UPDATE:
we finally figured it out! here's the solution for anyone curious or going through a similar situation:
- my friend downloaded every Microsoft Visual C++ Redistributables version from 2005 to 2015. turns out he didn't have all of those in his pc, and you can just get them in the official microsoft website;
- he then downloaded Swiftshader 3.0 Modified, which are just two files named d3d9.dll and Swiftshader that you need to put in the folder located at C:\Windows\Microsoft.NET\assembly\GAC_32\Microsoft.Xna.Framework.Graphics\v4.0_4.0.0.0__842cf8be1de50553;
- he also restarted the pc a lot during this process to make sure everything was running in his system.

and THAT WAS IT!!! the game now runs normally and launches in less than a minute! he's really really happy this is finally over, you have no idea. i had to try and help him more directly because he had already lost hope, but i wasn't buying it. it's his favourite game, he can't not play it bc of some dumb software issue to run a 2D game!
i hope it can help other people with similar issues in the future. if all tutorials you've tried before don't work, try these three simple steps i mentioned above! cheers :]