Firebase + react + telegram bot subscription system?

Question

Telegram

Hello! Please tell me in which direction to move ... The task is as follows: It is necessary to create a certain system of subscriptions. there is a bot through which the user enters the frequency in the cron format, and the address of the site from which he wants to receive screenshots, clicks save iiiiiii as I see it, a cloud scheduler function should be created with the cron parameters that the user entered, and trigger a certain cloud functions that already makes a screen and sends a screenshot to the bot, most likely... And perhaps you need to create a document in the firestore with fields like url, period, and another cloud function checks every minute if there are documents and then somehow compares the period, only then how to understand what period you need to run. .. in general, I've been struggling with this for the second week, while I'm trying to figure something out on pubsub, but I create everything with pens,