Change the coordinate system in After Effects
Have you tried the Sketch2Ae plugin by the Google Motion Design team? It works amazingly well. Here's a link to it:

https://google.github.io/sketch2ae/

I usually couple this plugin with the RepositionAnchorPoint plugin from aescripts, as Sketch2Ae seems to mess up anchor points. I personally prefer my anchor points to be aligned center to an element within AE. Here's a link to it: 

https://aescripts.com/repositionanchorpoint/

Once Sketch2Ae builds all your layers, select them all and reposition all anchor points with one click using this plugin. 

Both plugins are free, with RepositionAnchorPoint being optionally free.