how many
The sign "how many" is a "wh-q" sign. That means since it is a question that starts with the letters "wh" you should furrow your eyebrows a bit.
Note: If you want to sign "MANY" instead of HOW MANY, I'd start with the hands higher and a bit closer to my body. Then I'd move them outward an inch or two (instead of upward) while changing into the "five" handshapes. I wouldn't use the furrowed eyebrows for "many" instead I'd use a slight nod of the head.
Sign: HOW-MANY
Non-Manual Marker (Facial expressions and or body language): "Wh"-facial
expression