Lol. I train pretty much everything. My running and planks are fine, but I was struggling with push-ups so I’m going to ask advice something specifically for push-ups.
People struggle with different things. I was strong before I started, but not in ways that helped with push-ups. It took me over 6 months to train up to theoretically pass the PRT.
Where my strength lies is in running. On multiple occasions, I have trained from zero stamina to 10Ks in under 3 weeks with little difficulty. I had teammates in college that could roll up day one to our strength tests and whip out 15+ pull-ups and a 4+ minute plank without training but could barely run a mile .... we all played the same sport.... and genetics are weird.
For push-ups, I followed the 30's rule which is when you can do 30 wall push-ups, you can do 10 girl push-ups. When you can do 30 girl push-ups, you can do 10 regular push-ups. I have found it's very difficult for me to gain reps by doing regular push-up repeats. For me, what is most effective is doing as many regular push-ups as I can, followed by pushing myself with girl push-ups. This allows me to focus less on keeping form as I get tired, and more on getting reps in.
I'm no expert, but I've always been someone that wasn't great at push-ups and its been awesome for my training/improvement!