Upload Mass Inventory / Inventory Searchable

[NorthLightingCo]

Hey all, new Shopify user and new to e-commerce in general. 
I run an automotive lighting company and have been doing mostly sales through Facebook, however I am running short and time and want people to be able to shop my products on my website and automate the checkout for them. 

I have built my website and uploaded some products but find errors in my listings, broken images and some parts that are rejected. I am wondering what people use to upload mass quantities of products, several thousand at a time. 

Second, how are you all getting your products grouped and categorized? Searchable? 
For example; blinkers, search by vehicle, confirm fitment. etc. 

Thanks you.