Really frustrated...

I'm a bit frustrated with some stuff that I'm sure it's really simple to do and it's becoming so time-consuming.
I have a website where I sell downloadable items. The only thing I need is to put a f***ing "add to cart" button on each item and after paypal payment, the plugin send an auto email with the download link to the customer.

I've tried at least 10 plugins, but there's no way I can find one that does this simple thing, without complications.

Any tips, guys?

Thanks

The best tip is to hire some one to do this for you, maybe code it or find and install existing plugin.
If you have money then don't fuck with this. You would make more during this time.

Fiverr that is how I get stupid stuff like that finished