Hi @arko
While editing product you can add related product.
We will soon provide feature to add new product type in our application so that any one could add new product type.
For views, you can follow given link - https://forums.bagisto.com/topic/221/how-to-override-view-file-in-bagisto
For quantity in decimal, you need to customise it and we will look into this and in future will add decimal quantity.
Thanks
Rahul Shukla