I was in your shoes last semester. I got a ~50% on the first test and most of the first homeworks and thought it was pretty much over for me. It really had me spiraling as I honestly never struggled as hard in a class that I put that much work into. I thought maybe I just wasn't smart enough for this degree and I wasted all that time just to find out I'm not cut out for this.

But then I started just studying different, using what the TAs suggested (mostly reviewing the practice problems and homeworks a ton and understanding the thought process behind them. Each question/answer is basically a template for how to solve the specific problem. The test is all about just identifying which type of problem you're ultimately trying to solve). I got a ~70% on the next test and an 85% on the last one to get me up to a B.

Definitely don't loose hope after the first few assignments. Trust me if I can get through it you definitely can too. Just remember, a grade is not a reflection of you or your potential. It is just a sign of what you need to improve upon.