First of all, good for you for looking to improve your skills to better help your patients!
Second, a lot of things will come in time. Five months is not that long to be in L&D. Pay attention to other nurses and how they work with patients, things they say, and their behaviors. You will learn a lot this way. Keep in mind, everyone works with their patients differently. I know nurses that quietly encourage patients, saying things like, "that's great, keep going, keep pushing, keep it up, you've got it, that's the spot, right there," etc. Others count to ten, then offer some encouragement after the contraction. Others are like cheerleaders, really loud and cheery. I tend to ask my patients what is working for them. I will say, "how does the counting to ten work for you?".
Some courses may help- I took a doula course which was amazing for boosting my confidence.
One thing I learned over time is that "you cannot save everybody from everything". Basically a woman has to find her own energy and motivation to push, and not everybody will push well no matter what you do! Some might benefit from a rest, a small nap, or some juice, then to continue. Try changing positions, or encouraging her to visualize her baby descending, or holding her baby in her arms.
Keep trying! It will get better