Otek FS-502 negative scanner

I just bought Otek FS-502 hoping to scan heaps of old 35mm negative, but I am rather disappointed in the quality of the images I am getting, they are wishy/washy (not sharp or clear). After I have transferred it onto my PC the dimensions are 2544 x 1696 but the size of the file is 500-600KB whereas my normal digital photos are 2-3MB, which I assume is the problem. Am I expecting too much of this Scanner or have I not set up the scanning process correctly? Or is it dependent on the SD card, I have tried a couple with same result.
Also another problem has emerged when I emailed a couple of photos (saved from my digital camera) as attachments to a friend; when I open up my sent message, at the top (above the addressee headings) there is a message "OA removed access to the following unsafe attachments in your mail IMG_795.JPG". so all I have is the hugely enlarged image in the email itself.
Hopefully you can understand my 2 problems/issues an have some easy resolution.

Many Thanks

 

Your unsharp scans are caused probably by you not setting a high enough scan resolution in your Otek's scanning software.

 

Thanks pip22, but there is no obvious way (that I can see) to be able to adjust the scan resolution on the scanner. Are you able to guide with any specifics for this Otek scanner