"IQ" as a concept is much more hardwired. Your overall capacity for certain things like pattern recognition if you were a truly stupid individual would always be diminished and you'd always have to work harder, however it is still possible to overcome one's own limitations through hard work, at times in a way that "smarter" individuals will not namely because they are lazier. It reminds me, loosely, of Napoleon complex guys achieving much while the handsome jock may while away his time getting laid and being debauched and thus fail later in life, or the tortoise and the hare, or the story of Mike Tyson. You see Tyson got bullied a lot as a kid and his chief motivation for becoming a fighter and the first fight he got in was because some kid ripped off his pet pigeon's head. Now he's world heavy weight champion and can afford to keep as many pigeons as he fucking wants and be left in peace.
There is a degree to which one can always compensate for their deficits, and often times people will end up vastly overcompensating for them. The overwhelming underriding drive here is "I'm still not good enough." So basically while someone else might be doing stupid shit like getting high and playing videogames while engaging in pointless navel gazing with their high school buddies, if you maintain that internalized drive to better yourself it's possible the allegedly IQ120 kid is just going to atrophy into mediocrity at best, whereas you otoh will have bettered yourself into being a well read and perhaps scholarly man. The difference is just that you'll have way more difficulty in that area, chiefly of overcoming your own frustrations and converting that anger into Drive.
It's like having weak as shit genes for strength in a sense. You might have a predisposition to becoming fat, or of never building muscle tone, and maybe you will never aspire to the same heights as those born athletes, but nothing is stopping that athlete from leading a sedentary existence eating pastries and burgers and just turning into a disgusting fatass whereas the person who maybe needs to out three times the effort into it can still get super strong and become cultured. Nature is only part of the struggle. A critical part, but still only a part. So if you spend all your time reading, doing puzzles, and trying to learn a new language or three, you're still going to end up being "smarter" or far more intellectual than someone who otherwise might be smarter than you.
A key thing is obviously not wasting your time on trash like k*hl or the internet in general for the matter especially Twitter, or dumb YT videos or celebrities or whatnot. Read literature. Watch good documentaries. Understand the basics of concepts and work your way up to more advanced concepts. Read wikipedia articles for fun.
It's like everything else. Shitty IBs are the mental equivalent of junk food. If you consume nothing but trash you'll feel like trash and operate like trash. It requires the discipline that I frankly lack and has dragged me deeply down into the mud to abstain from the immediate gratification and focus on the less pleasurable task at hand for a plausible future reward. You can still better yourself physically for example by working out but if you do nothing but consume twinkies and fried chicken and coca cola all day then you're just working against yourself.
Find something like the mental equivalent of low weights before working up. Force yourself off the slob couch of imageboards and go to something familiar enough like wikipedia. Just keep clicking random links and reading about random things. Work your way up to the citations and references section of the article. Get to the point where you can take books out of the library. Learn more in depth about some chosen topic and try forcing yourself to stick with it. Don't move on until you feel a bit of mastery, and when you do, make sure to find something that challenges that sense of mastery (as iirc brick said in another thread, or maybe the american I forget re: dunning effect etc.)
Try taking up math. Start with the simpler concepts. You wouldnt expect to start benching 350 lbs so dont get discouraged and frustrated when you can't make sense of advanced algebra or speak German fluently or whatever. Learn to avoid junk food like the plague online. I have not been doing this and I feel massively dumber and just trashier and unhealthier as a result. EC at least has been helping to wean me off that and provided a refreshing sense of my own stupidity.
A key detail is if the people around you are making you feel stupid, you're in the right place. I still remember my first weeks of college where I went from feeling like some kind of intellectual in my high school to feeling dumb as a brick of shit my first semester. I felt completely untalented and stupid. Maybe it's still true in a sense, but it forced me most importantly to have more discipline and to sharpen my mind a bit, rather than the fatal poison of self satisfaction. Never let yourself feel self satisfied in anything, Ernst. If you want one thing of your enemies, it should be for them to feel that for extended amounts of time. Let others make you feel dumb or weak and try to catch up with them, challenge yourself, learn real satisfaction from the surmounting of great personal challenges, and be humble enough to start small and disciplined enough on the follow through.
If you already feel dumb you're on the right path. Just don't beat yourself up, beyond the way you'd beat pig iron into a fine sword.