Jinfinance split and 50-200

Hi! I wanna start buying a couple of manual lenses to use along with my K-r. The only manual lens i currently have is a 50mm 1.7.
My stock screen is scratched (obviously my fault), its distracting, but...
Anyway, do you guys think it's worth for me to buy a jinfinance split screen?

I'm 14 years old and i've never used a SLR Camera, so i have never used a split screen.

Do you guys think that the focus gets THAT much easier than with catch in focus? Since my screen is scratched, is it worth to replace it with the jinfinance screen? Does it blackout in low light with 18-55 and 50-200 at f5.6?
Thank you alot