gestrichelte Linie animieren

1. Draw a SHAPE line (NOT a mask!)
2. Set FILL property to transparent, and STROKE to the color you want.
3. Twirl down the properties on the shape layer > Contents > Stroke 1.  In here, you'll see a property called DASHES. Click the + sign behind it to add it to your shape properties.
4. Now simply set the Width you'd like, and play with the "dash" amount property to get the look you want.
By default, the dashes will be at a right angle to the base line.  If you want the slanted look, simply go to the Transform properties of the shape layer, and twirl the SKEW property to whatever look you're going for.
5. To animate, simply use 2 keyframes on the Dash Offset property.

Done!  ;-)

There are thousands/millions of ways to draw a dashed line. I suggest you look for a reference image/animation to share, here. Then, it'll much easier for someone to assist you.