bro my PC takes forever to do literally anything

ok guys i really need some help here. my PC has been dead slow for like the past month and i genuinely dont know whats going on. like i click on chrome and it takes forever to open. open a game and it just stutters the whole time. even moving files around feels laggy

checked the temps and everything looks fine. no weird noises from the fans or anything like that

been browsing around on Amazon, eBay and Orangehardwares looking at some options but honestly still not sure what i actually need to get

my mate reckons its the hard drive and i should swap it out for an SSD. another mate says its probably the RAM. honestly have no idea who to believe lol

has anyone dealt with this kind of thing before? like what do you check first when your PC just randomly starts being slow. really dont wanna take it to a shop if i can sort it myself

any advice would be class