Hello meheso,
your second & third scan are pretty close, maybe just do less at a time. It looks like you have adjustments in the scanning program you are already operating in, maybe just play around with that a bit. If you can narrow down the scan area on the scanner to just one corner & scan just a quarter of a sheet at a time you may find it works better. But I'm no computer expert either ;)
Here's a few scans to show you what you are up against, I picked a couple you have already shown, so you can get an idea of how hard it is for the good people here to tell what you have in your sheets.
First Denmark "hook on spar", left stamp, 1938 I think, this little detail takes it from probably a 20 cent stamp to over $150 in good condition.


This next one is a Chinese reprint as far as I know, easiest way to pick them but not the only way, is the dot in the button between the gap in the collar ;) Without the dot these are very sort after.
A lot of the PRC (Peoples republic of China) stamps have a high CV if they are not the reprints. You are going to be busy so take your time ;) Those flag stamps on the same sheet are worth checking too, but their harder, & I can't help you much as I still have 4 of those I don't know which they are


Will have to leave you with it for now, good luck.....Jad