That’s hard to say, what you need to change, if we don’t know what your settings are now…
But the first thing I’d do, is to check your Outliner, to see if you have anything disabled in the Viewport, that is still Rendering (like Lights, for instance), or the other way around (Objects blocking light, that aren’t being Rendered.
Also, are you using any Compositing Nodes?
And like Omar said, don’t use Material Preview.
