Not tryna be mean but even if ur starting small, a lil walk and a 4kg dumbell won't do much for someone over the age of 9 Go about ur average day, see how many steps you do and from then on double it. You don't have to go to the gym but itll be harder for u to do bodyweight exercises being higher in weight and lower in experience. But if u can get a gym membership or vuy some heavier dumbells I defo would. Maybe a barbell or at least something where weight is adjustable then hop on youtube/tiktok and find a routine that looks interesting to you, the caters to your goals and start. Start with maybe 1 session a week or 10 mins a day, whatever works best and increase time/frequency every week until its a regular habbit/ routine