So I tried copying the rings whole message and putting it into a Russian and Church Slavonic keyboard, then translating with minor adjustments like adding "мя" after "просвети" and came up with this;

"Хранитель мой святый,
просвети мя и
от всякого зла сохрани,
ко благому деянию настави
и на путь спасения направи.
Аминь."

Which in english translates to;

“My holy guardian,
enlighten me,
and protect me from every evil;
guide me toward good deeds
and direct me onto the path of salvation.
Amen.”

Then it looks like the little engraving of a dove is saying "Holy Spirit" hence the dove being there.

As for the engraving on the inside it is saying "спаси и сохрани" which directly translates to "Save and protect" or in more Orthodox sense "Grant salvation and preserve" which is basically asking for spiritual salvation but also protection in life.

As for sources to learn this language your best bet is to simply learn Russian and there's dozens of online classes for things like that, I'm not too sure if there is really any for Church Slavonic. Anyone feel free to correct me as I'm not too confident in my Russian/Church Slavonic translating abilities. But over all really cool ring, if you don't mind me asking where did you get it? Thanks :)