It all depends on the options you have with the API.
Sometimes it can be as easy as setting a webhook, and sometimes you need to poll the data and check for deletions. Which can also be done in multiple ways depending on the data the API gives you.
Hey @ivansergeev, welcome to the community. As @BramKn mentioned it would be nice which CRM you’re trying to work with to see what their API has to offer. Generally, most of the time it’s best to start a scheduled workflow that e.g. looks for new closed projects to notify you with. Maybe you can add some more contect on wich CRM you’re using?