it will take you months to reach aguero's physique, considering you said your build is more like messi at the moment, to be honest you should focus on your lower body strength since you're fast (maybe build a good squat and do some plyometrics and vertical jumps), and placing your body between the ball and the defender, because you won't be able to compete with centre backs physically at 5'5", regardless of how big you are (aguero is 5'9") so working on drawing fouls could be an asset, look at how players like messi and hazard shield the ball and get so many free kicks from them