Spoken languages are linear. Sign languages are not. The grammar is very different. Sign languages have multiple articulators: two hands, face, eye gaze direct

Spoken languages are linear. Sign languages are not. The grammar is very different. Sign languages have multiple articulators: two hands, face, eye gaze direction, shoulders, trunk. These can all work together to show multiple things at the same time. Spoken languages can really do only one thing at a time (with a few minor suprasegmentals such as tone). You can construct a signed version of a spoken language, which may be useful for things like quoting book titles and other cases where you need to represent the exact words of a spoken language in signed form, but it's not common to use that for everyday communication, because the hands move a lot slower than the small muscles of the mouth and throat. (Linguistics is a fascination of mine. Sign language linguistics are especially interesting.)