need solution for Freshsales- vendor and customer triggers

I've been experimenting with several CRMs over the past few years like Active Campaign and now Freshsales. They seem to fall short when it comes to my needs of having the ability for both my customers and vendors to trigger an action resulting in a fully automated sales process. I am working with a student housing business. Basically an air bnb for students. Our goal is to have the application process automated. The dilemma is that we have the student side and the landlord side that both make decisions per single transaction. We are aiming to have these decisions trigger the next step in an automation.

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Actual breakdown: Once the customer (student) applies online at our website, the vendor (landlord) is sent an email with application details and a request to confirm availability. A link to a shared google sheet is in the email where the landlord can select a list of options in a drop down menu. "Small Room, medium room, large room, or no availability". Once one of the options is selected, zapier will update a contact field in Fresh Sales. An email in Fresh Sales is triggered and sent to the student which includes the landlord's room selection. Now the student has to "accept" or "decline" the room selection offered in the email. This is where I don't know how to create a trigger action that will update a field in the student's contact page.

I realize that the CRMS I am experimenting with are not designed for 3rd party triggers or interaction but I was hoping I could find some platform that could be integrated via zapier allowing to accomplish my automation goal.