Your problem isn't in the opening. Let's say, Ruy Lopez, you're playing as white is definitely good opening! On this level you don't need to know opening lines. You can play opening stage of the game just on opening and general chess principles. But, most likely you don't know what i'm talking about.
In general, you are weak everywhere, not only in the opening. Thus, there is no reason to concentrate your efforts only here. And, on this level, if you want to improve, you need more practice. Few blitz games per week is nothing. Solve tactics. 5-10 puzzles per day would be nice. And play games with longer time control, 15+10 or longer. 2-3 games per day is enough. Also would be nice if you could learn from your mistakes. Problem here is that it's hard to understand for beginner what is mistake and what is not. So, you have to either improve your general chess understanding (watch video lessons, read books, etc.) or ask somebody to explain nuances for you.
Wish you good luck in you chess journey!
I feel like I'm always on the defensive and spend a lot of time trying to find good moves and get low on time a lot. Are gambits a solid options to put big pressure on your opponent early? What are your blitz strats?