Observe how other platforms are designed, ideally ones that operate in your same business area.
I recommend you create an account on a web application similar to the one you are designing and see how that product was designed.
Resize the browser, or right-click and click "Inspect". See how the elements behave. The header will stretch the whole width, whereas inside widgets will expand with the grid up to a (probably) max-width.
You can also click
- sign - this will scale the view so that you can watch how it behaves to 1920.
Try using Google Firebase or Google Analytics.
I suppose being a web-app that works on that wide screens it will likely have a dashboard and widgets. I would align the widgets width up to a max one so that they don't stretch the whole width, after that they line up in the same row. Perhaps try using wider gutters and margins ( 24px and 32px respect.) on wider screens and (16 and 24px respect) on narrower ones, that will also help give room to breathe.