I learned Hieratic at university as part of my MA degree. It required me knowing Old, Middle, and Late Egyptian before I even started to learn it because you have to know what it is you're looking at. I don't know of anywhere you can learn it properly outside of an academic institution.
No, it's not a one to one conversion. I said it's like shorthand, and I meant that. Each sign has its own form, but it's not necessarily anything like the sign it represents. They're quick forms of the signs, designed to be written in ink rather than carved in stone (because they really didn't write in full glyphs in ink unless they were doing something special like a Book of the Dead, and even then that's called Cursive Hieroglyphs) and often they're just lines because there's an assumption that the reader is familiar with what *should* be there.
The second image here is the *original* text, whereas the first image is the transcribed version into hieroglyphs which is easier for most Egyptologists to parse than the Hieratic original.
Some signs *might* look like their hieroglyphic counterpart, but the majority of them have a different form all together, and you have to be able to parse that. For instance, you have to know what you're looking at to understand that:
The full section is easier, but you still have to know some things:
You've really got to know what you're looking at to understand that the edge of the cartouche, the sun symbol, and the wsr (jackal head on a stick) symbol are all rolled into that sign that looks like a 13.
It's one for one on the number of marks on the page but not for what it looks like, and it all depends on the handwriting too. Some are better at writing than others, and some had more time to write. The text above is a legal text recorded at the time the trials were happening, so it's quick and messy. Something like P.Ebers, a medical papyrus, is much neater because it was copied up cleanly.
