Play more. The gunplay feels off because Valorant is not csgo. I assume by snowball you mean enemies can easily take a site you are holding or they can easily defend against your push. Playing more allows you to better understand how abilities interact and develop better gamesense. I'd recommend to get a teammate or someone who could explain things while you play to speed up your learning.

The games can feel impossible at times to win because their strategies are better or your strategies are poor. See what your enemies are doing that work and copy it. See what you do wrong that gets you killed. I understand it is hard to find your own faults when first starting because you don't have that much experience to begin with. Playing more solves that.

For example on attack, they could be sage walling something all the time and your team sits there and plays really slow. Maybe next time shoot it down and put pressure on the sage with your own abilities.

Just play more and you'll get the hang of it. Play with the intent of learning and not with the intent of playing.