Sign language IS pretty universal. The only differences are mostly regarding the order in which they are shown to produce thoughts.

I learned SEE (Sign Exact English) and ASL (American Sign Language). SEE was so when teaching children we could teach sentence structure for writing and reading. However, it's nearly impossible to use SEE all the time. Your hands and fingers would get so exhausted!

And ASL is the more useful conversation language. It's literally shaping your thoughts into being. This makes the most sense to me. I used to dream in sign language as a kid, so when I decided to take it in college it was just THERE. I was like a savant.

Oh! And I knew a tiny bit of French and Spanish at the time and looked in the French and Spanish versions of sign. VERY similar.

Sorry for the long explanation... that you didn't ask for. LOL!