Xbox constantly crashing when playing Multiplayer games

Hello all, so to let you guys in on the situation, basically 2 years ago i bought a used Xbox with a couple games on ebay for a really good price. And I have noticed that this xbox has trouble sometimes playing graphic intensive multiplayer games. For example,
i used to be able to play Overwatch, fortnite, and other multiplayer games back in the day, and it was
fine. Meaning it wouldn’t ever crash, and if it lagged it was because if the Wifi. But here’s the catch. Whenever I play the online version of GTA5, it tends to crash alot more often. I noticed
this earlier likes months ago, and over the last couple of weeks I have tried played with an External cooling fan hooked up specifically for cooling down the xbox. I did this because i noticed everytime it crashed the xbox vents would be piping hot as well,
so i thought it was an overheating issue. But the only difference it made was that i could play for longer periods of times
by myself on GTA Online. And even with that there were times where it still crashed, and then xbox would say “error, this game could not be found, please reinstall and try again“ when i tried re launching it. Also,
whenever i played people in real time in gta online, you could always bet money that the xbox would crash at some point, and you’d be right. I even noticed that the xbox would crash in certain places too consistently, like after a cutscene, or whenever i crashed
the car in game, etc. Lastly, when playing Gta online there would be frequent lag spikes, where my game would freeze on a frame for 5-10 seconds, and then eventually, the screen would respond and continue to show the game animations. So all of these points
lead me to conclude that there is either a problem with the amount of RAM my Xbox has, or the quality of the graphics card. Because i have asked around and no one else has this serious of an issue, and the cooling fan didn’t fully solve this problem as i had
hoped. Thus this leads me to believe this is a hardware issue. However, i checked my Xbox’s serial number and
sadly isn’t replaceable by a warranty. Thus, i would like to ask this community for help in how to fix this, and whether or not my diagnosis is accurate. I would prefer not to buy an Xbox,
but i would also like to be able to play GTA Online without interruptions.

Thank you guys for your patience and time.

:)