i think my msi pc is having a stroke genuinly

okay ill try to list everything wrong with the pc since it started acting like this first of all i have an msi katana gf76 11UC 11 gen intel(r) core i5-11400H@2.70GHz it has 8GB of installed ram 4 gb graphics card and im using 115GB out of 943 GB . (these are the graphics cards : NVIDIA GeForce RTX 3050 Laptop GPU (4 GB) Intel(R) UHD Graphics (128 MB)) .

now the probleùms started like 2-3 monthes ago the pc started getting laggy and im getting 80-90 fps in games i used to get 230 fps in and the a bit later the right fan started making noise like a litteral machine gun so i sent it to the repair man and he replaced it for me and after i got the pc i noticed i has gotten way laggier i cant do anything without the screen lagging even watching youtube make the pc lag and the audio too . so i did what anyone would do i thought it was a virus and factory reset the pc thru a yt tut since im not very good with pcs honestly so after that it was good for like a day then it started lagging again so i optimized everything on the pc to high preformance mode and it seemed to fix the issue kinda but now it overheats alot + everytime i play a game or anything if alot of things are happening on the screen like vfx of me shooting a gun etc the whole screen goes black for about half a second the comes back and it goes on till the thing im doing is gone and there is nothing on screen or it goes black 3 times in a row then it goes backk to normal also i cant run anything on more than 80 fps now (roblox and minecraft i cant bring my self to try anything bigger) and they lag now too while like 3-4 years ago when i got the pc i could run gta 5 online on it smotthly with no lag almost. also i noticed today that its using alot of my wifi like a very considerable amounta i share a router with my family when i was using the pc it was so slow but as sson as i closed it it went back to normal . can someone help me or reccomend what do i do is this a virus or malware or trojan or something mining crypto on my pc please help