And what happens when there are different studies with different results for the same (or similar) topics?

Impossible. Either there are some external variables that were unaccounted for, or something is not deterministic with our current level of understanding, or someone made some errors in their experiments, or someone doesn't know how to construct hypotheses. These are not matters of opinion, but matters of reproducible experiments and verifiable facts.

And sure, throughout history there were plenty of cases where things happened and we rejected some long standing hypotheses, but that's because someone came up with verifiable alternative that can be confirmed with repeatable experiments by anyone willing to do so.

Flat earthers and other conspiracy nutcases, though? When presented with scientific, verifiable evidence, their counterarguments boil down to "you must be in on the conspiracy". That's not a healthy discussion - that's a waste of time.

They won't listen to logic and facts.

I've heard a great expression for that: you can't reason some out of a position they didn't reason themselves into.

The greatest discovery/invention in history of mankind: scientific method