Please keep this forum in English.
Using mods should be as simple as installing Forge (you get the installer from our Files page) and dropping your mods into [Game Directory]\mods where [Game Directory] is selected by the "Installation" (I'm still annoyed about Mojang's naming of them, they're more like Profiles or Instances) and is defaulted to .minecraft.
Do not learn Java through modding, it will be harder than learning it properly and will almost certainly corrupt you with bad practices before you've even started.
This is not something that will be discussed, we do not provide basic Java education, we expect you to already have that.
Have you played with infernal mobs in the past?
Have you never set the Game Directory of any of your "Installations"?
Have you never cleaned out .minecraft/config?
Wonderful I had to track it down manually because atomicstryker isn't using the Forge config system...
C:\Users\ophel\AppData\Roaming\.minecraft\config\infernalmobs.cfg
Proxies were used to separate side-specific actions so you weren't calling client-only code on the server where it wouldn't exist and would cause a crash.
Nowadays that is handled mostly by sided event handlers.
Everything you have in your proxies can be common or handled by sided event handlers.
Most YouTube tutorials you'll find are utter crap. They tend to be "monkey see monkey do" and don't teach anything... they just go "do this, it works" and we get people wondering why it doesn't work when their issue is basic Java skills. Yes I could rant even more about this but I'd rather not.
No, you should separate your modpacks into separate game directories, the game directory being the folder with the mods, logs, saves, etc. folders in it.
Are you following a tutorial of some sort? Proxies are an old pattern and there are now better ways to do what they used to do, also your use of them completely ignores the purpose of them.