incremental refresh on custom connector

hi, i have built a custom connector that is working very well. it calls a rest api that i own and it gives the data while paginating so i am able to transfer large amount of data well. i have two questions for which need some pointers:

1. how can i show message while data is being refreshed. i batch send records from api and ask for next batch but i am not sure how i can show a message to the user ..like 1000 rows received, 2000 and so on.

2. how can i set up incremental refresh. i can do anything on service side so any pointers here will be helpful.