Hitting your opponent is only part of the battle. You know you need to improve and you're willing to learn how; you're already making steps in the right direction. Stay positive; it can have an impact on how you play.
With that being said, learn different ways to approach different situations. For example, instead of determining that the only way to counter projectile spam is to use it yourself, try to figure out how to play around it. That is, figure out when to block, spot dodge, approach, jump, and counter attack. Take time to analyze your opponents' behavior; try to learn to think on the fly. Avoid repetition. Ask yourself: what works? When? From there, try to learn basic mixups/combos.
I suggest picking characters that help with practicing fundamentals like Pit or Mario. Or picking a character you like and exclusively training with them until you feel like you've improved. I think fighting Amiibos helps for beginners, too. Good or bad, they kinda mimic your habits, and it's like fighting yourself once they level up.
Good luck.