How can I reset segments and remove multiple contacts on an ecommerce platform?

[DaphneSG]

Hi,

if anyone know how can I approach Shopify admin or customer service for the below  2 questions:

1, i have 8000+ contacts there and want to remove the segments on all of them, or reset the segments.

how can i get this updates instead of keep " added" new segments to the current contacts?

2, how can i remove multiple contacts via csv import or any other way?

obviously, i cant find anyway to remove some of the contacts and it shows error.

3, when i send the marketing email, I found that its error if i select all the contacts, maybe 8000+., 

if there is a limitation on daily send or per marketing email send?

thanks all