I made a comment on how to fix that, hope it helps.
So if you have paid for and downloaded it, go into the files and open the among-us-windows one. After that, open the next file. Do that until you get to Among Us, which looks like an installer icon. Right click that and click 'Open'. It will ask you to extract some files, but if it opens another window after the extraction is done, just press the bottom Tab thing on it.
Otherwise, just wait for it to extract. Now, it will send you back to one file, keep opening it until you get to the actual Among Us logo. Right click, open it and wait for it to load. Hope I helped.