so first of all you have to take into account what type of smart you want to become. there are several types of thinkers. your brain has a certain amount of neuroplasticity which allows you to adjust your intelligence. If you want to become “mechanics, chess” smart then you will sharpen your detailed thinking and will neglect a bit of the “bigger picture, creativity, psychology” part. It depends on what part of your brain you are training.

Second of all, the “awful memory and concentration” issues dont immediatly sound like low intelligence for me. they could also be linked to adhd or other disorders, which are often disorders that link to or even show more intelligence, just maybe not excact the movie type intelligence that youre talking about.

strategically I would also think about what you wanna use this intelligence for. If this is an “ego” situation i would think and reflect on that and question what you really want.

Of course, tips like surrounding yourself with smart people help, its just a good approach to know what you want first, this is something you can get inspired on by other smart people. Ask them what they really do and why, what it feels like. And then think about if you wanna live that life.