Extreme trouble editing music because MuseScore doesn't have the time signature correct

I scanned a piece and created a very clean, clear PDF file. The PDF was then converted to a MuseScore format which I downloaded. I have spent two days trying to correct the mistakes in the piece so I can ultimately transpose it. However, MuseScore seems to think that a measure has either one beat or three beats - not two. Every time I try to change an incorrect measure, this counting screws up successive measures. I end up undoing the change and trying to figure out a different way to make the change. This is absurd and I think the PDF conversion software really failed. What can I do because I'm ready to abandon MuseScore.

In the uploaded file, the F# indicator after the bar line at the end of the first staff shouldn't be there and I can't delete it. Measure 20 (contains two eighth rests which equals 1 beat, not 2) is what I get trying to add to the measure to get eighth rest, eighth note, eighth rest, eighth note. I tried to upload the PDF that was originally converted but your form wouldn't take a second file.

So what is going on???