Haha, you fell for Pi scam, just like I did. Well, I had RPi one and it's in no way imaginable usable for everyday things. Just opening random web pages takes over minute (yep, I don't exagerrate and the max I saw was almost 5 minutes) with adblock on too. You can't play videos too well either, because hur durr Broadcom either doesn't make drivers or makes only crappy ones. And while big thing about it was running Quake, it couldn't do that. Stock it ran Quake at 10 fps, overclocked a lot (pat 1GHz, which is like 60% overclock) it barely reached 14 fps average. It was nowhere close to being fast enough. Overall it was nearly unusable for anything. The only things that ran well was OpenTTD (without GUI and even then as CiNEmAtIC ~30 fps) and some Risc OS games that are literally simpler than minesweeper. In short, it was seriously insufferable experience overall and not even cheap one. Now RPi 4 is times faster than Pi 1, but it still uses very old Cortex A72 cores and only 4 of them. It might be just enough for reasonably not terrible web browsing experience, perhaps some light productivity, but Broadcom shitty drivers strike again and this time ruin YT playback at anything past 480p. Any task requiring some CPU grunt will consistently take a very long time to complete and yeah, some crappy 100 USD Android phone might even beat RPi 4, while giving you screen, battery, storage, more comms. Gaming is still rough on RPi 4, sure some things could be emulated, but PS1 is basically max it will do and even then not everything. It can run Half Life 1. Basically some Pentium D era SFF prebuilt computer with something like GT 710 will do way better at basically everything than Pi.
I think that Pi foundation is basically selling overpriced e-waste for huge premium, but if you view Pi as it originally was, a small SBC for embedded use and cheap and simple programmable computer to use in some project, but you don't want more sensible micro controller like Arduino, then Pi is for you, but it was never meant to work as desktop and very unsurprisingly sucks at that. If you wanted small, low power consumption desktop computer, that is actually usable, then used thin client computer or micro computer or nettop would have been a lot better. I have seen 7th gen i5 machines with 8GB RAM and some SSD going for 150 USD on eBay. They have quite nimble CPUs, adequate graphics and wattage usually bellow 25 watts. Phil from Phil's computer lab at YT does some videos about some machines like that and they can run older games and typical daily computing stuff just fine.
Anyway, beyond performance, other problems aren't exactly normal and shouldn't exist. If you haven't done that already, I think you should just reflash memory card and see if problems persist, if they do, then try another brick or bigger cooler, see what happens, if nothing changes and you still have issues, just RMA it. Audio problems might exist due to standard Pi OS fucking things up with audio drivers. I had to deal with that bullshit myself and made it work after being in forums for way longer than I should have, it might be solvable, but I have no clue how to do that. Forums might be helpful, but expect some nerds that are impossible to communicate with.