Kinda confused... Where do I start?

[Trainer Monkey]

Understood, but I want to be a fighter, I just need to gain weight and mass to do it.

By gaining weight you are sacrificing a huge natural advantage in boxing competition; in terms of height and reach.

I'm sorry, but I don't know what you mean?

What he's going for,is if you can learn to drive with your hips,and stay down in weight, you can stay down in weight class
If you can do that you should have reach in your division,which means you can pepper your opponent,and if your throwing your punches right,you'll maintain speed
Not everyone has the build to be a Heavyweight,play to your natural advantages,Tommy Hearns had a very long career doing that