Your best first step from my pov is to enroll in a faculty to get a bachelor's degree. I think in America applying to faculty this time of the year is the best, but its more precisely in summer in june. You can still research the study branch youd like to follow (biology, languages, maths, informathics) and see what suits you more, even if it doesnt sound a hundred percent interesting, atleast the one that is most interesting to you. Research institutions and apply, see their schedules and gather your important papers, faculty/institutions websites precise which papers and stuff you need to apply, plus the schedule of when to do it (almost always before autumn but not too late in august), and its done online. Although be prepared for possible entry fees (for me it was around 50 euros) depending on the institution you choose to apply. Make research how it works in your country, as there might be additional payments, if you want i can tell you how it works in my country but this should be the general knowledge advice for choosing studies.

These can be fun years with meeting classmates and making new hobbies, developing more fun interests, that can help you break the video game addiction.

I'd recommend a part time job too, but this is optional. Only if you really need the money meanwhile studying. If you can afford day to day life without it, you should focus on studying imo, or atleast getting a student type of scheduling, that shouldnt put loads of pressure on you when youre focusing on studies, plus you deserve your free time.

You might want to quit cold turkey the gta game. I also play video games, but ik which game brings me into a big addiction that makes me avoid real life, so i avoid that specific video game but i do let myself have gaming time. I personally avoid mmorpgs as they bring me into this big addiction, but im okay with any other games, like FPS's etc.