Przez tą modyfikację, gdy włączam Minecraft wyświetla się to:

Korzystam z dobrej wersji gry( 1.12) , ale nie wiem, czy to jest spowodowane tym, że używam złej wersji Forge, bo NIE NAPISALIŚCIE TEGO.
To może być spowodowane tym, że korzystam z "crystal laucher":

Z góry dziękuje.

I don't speak Polish, but from what I got from Google Translate and your screenshots, it sounds like you need Minecraft 1.12.2, not 1.12. Also, if the first screenshot is anything to go off of, you need iChunUtil as well, which can be found here: (https://www.curseforge.com/minecraft/mc-mods/ichunutil/files)

Thanks, but this time it displays:

PS. I also relied on the google translator.
PPS. And you will say what version of forge?

I'm using version 2838 for Forge, it's the latest version: https://bit.ly/2wKFydt

I honestly don't know how to fix the problem you have, so instead I'm going to post a download link for my "mods" folder: https://bit.ly/2LxoMrv

Here's some instructions if you're unsure how to proceed (I wrote them in Polish so you don't need to worry about translating everything):

Hope it works! Definitely post again if it does not, although I must admit I likely won't be able to help again as I have done all that I really know how to do.

Wery thanks.