I'm 16 and want to improve my life

I'm 16 this year and I feel like I've been completely wasting my life, sure I've been successful in some parts of life but others not so much

I have a very pretty girlfriend and we've been together for a long time, she's fit and very beautiful but I'm like a goon standing next to her.

I want to know how I can start improving myself physically and perhaps financially. I'm around 75kgs and 5'11 and skinny fat. I'd love advice on how to gain muscle while gaining weight as well.

if anybody knows a good way I can make some money online that'd be absolutely fantastic as well (please don't scam me)