Bulk update of inventory

Right now i use ShopifySharp and update them through the rest api, one at a time. Im worried this will be so slow i cant add more products.

I really try to only make one call per style tho. But its still slow. Right now i have about 2000 variants and if i can update 2 per second (and i cant) it will take half an hour. That is way to slow.

I have not checked any apps, is there anything that can be automated?