I've spent all day trying to work this out, but frankly this translation is too rough for me to make a lot of sense of it. As best I can tell:
1) Formialuka (sp?) is the Creator, but inexperienced at running a world
2) There are other deities in the world; "goddesses" are mentioned and one addresses is shown addressing Formialuka as Senpai
3) The deities are powered by belief/worship, and can lose strength (and perhaps vanish) if they don't have enough worshippers
4) Formialuka, as the Creator, can't lose all of her strength if she's no longer worshiped, but she can be weakened and outclassed by other deities
5) Baros is the first hero, who gained a lot of worship by defeating the Demon King. This led him to become arrogant and greedy, and he's been stealing skills that Formialuka gave otherworlders in order to increase his own power
6) It is really damn unclear just what Baros is. I can't parse whether he's ascended to being a god after death, is some kind of living demi-god, or something else entirely
7) No matter what he is, the worship of Baros has made him powerful enough that Formialuka is unable to just strip him of his powers
As for why Baros is too powerful for Formialuka to deal with, it seems that worship of Baros is widespread (particularly in asshole kingdoms like Teyran) due to being a former Hero, but the common people have forgotten Formialuka.
Obviously some people still know she exists, namely otherworlders who've met her, certain nobles (like the king of Teyran), and the priests/sages/wizards/whatever who do the summoning, but I'd be willing to bet that they don't actually worship her and just push her around since she's such a softy.
At least that's the best I can make out of this mess.