What did Shouko sign to Shouya in Koe No Katachi volume 7, chapter 54?
Note: the below images are the signs that she used, in the order that they appear (right to left).
So I watched the limited theatrical release today. While I can't say that I recall anything verbatim, I'll be updating my answer from here.
Shouko says, not signs, in the movie, that
She believed that if she weren't around anymore, everything would be better, which is what led her to attempt suicide in the first place.
This tears into the heart of the matter: the immense guilt and discomfort that Shouko feels about the entire situation, which is what led her to make that decision.
Also, this highlights a point in which the film diverges from the manga, so take this with a grain of salt.
While I can't interpret JSL very well, we can infer what happened through the use of context clues a few chapters earlier.
This happened after Shoya effectively saved Shouko's life, when she attempted to jump off her balcony into the river below. Recall in an earlier chapter, Shouko and Shoya swapped positions, effectively keeping her on the balcony, and him plummeting to the water below.
From that, what we can infer is...
Shouko thought that Shoya was dead, and was feeling incredibly remorseful for attempting suicide, and that Shoya had been badly injured due to her actions. She's frantically apologizing and is grateful that he's alive.
I found a good sources to answer this question These are from the chapter 54, page 9,10,and 11.
Page 9, third panel.
You - Fall Down
"You Fell down"
Page 9, fourth panel.
Me - Bad
Page 10, first panel.
"(At that time) same"
Page 10, second panel. ( Not sure about this one )
"I think that it is the lowest"
Page 10, fourth panel ( Not sure about this one too )
"I messed up my relationship with everyone"
Page 10, fifth panel ( and this one too )
Past - Same
"At that time (when I was in elementary school) and I have not changed"
Page 10, seventh and eight panel ( and this one too )
"Everyone is Important ... "Based on(?)"
References(Japanese's site) : los-endos.hatenablog.com(Japanese)