Best way to represent hundreds of rows – marketing calendar

I am creating a UI similar to a marketing calendar. But it has hundreds of rows, each row showing a bar that represents how long the process took. So the table header represents time (weekly, monthly, quarterly). As you can infer, monthly and quarterly view will grow exponentially.

Image attached for reference.

What would be best way to represent such information. The aim is to show summary in a visual way (rather than textual) and allow user to dig deeper if he prefers to.

Edit (1):

I am adding more details since my question seems too vague. In the image lets look at the y axis. There are 100's of tasks that was done by someone. Now these tasks belong to a certain sub department which in turn belong to a certain department. The problem is there are a lot of rows to scroll through to get the overview of the information.

How many tasks were finished under a certain time?

If I take a cards based approach I can show the gist of this interactive table but if I want more information I need to come back to the tabular view.

My question is what is the trade-off between usability and readability? How to condense the information in this rows of data such that there is a balance between usability and readability?