Here is the view in Photoshop with 100% Zoom

Here is the view in Photoshop with Full Image Size

Here is the view in Windows Photoviewer (It's Zoomed because if it's not you can't see that it's blurred)

Here is the View in Unity

And Finaly this is the Original Image Saved in Photoshop as PNG

I hope the pictures have made the situation clearer and I hope that you can help me better
Kind regards
Max
The blurriness is produced by the other programs scaling up a tiny image. The view in Photoshop at 100% is the only accurate view. Your "full image size" view is about 2600%. If you want your image to lok like that in other programs, use Image > Image Size (Alt+Ctrl+I), with Width and Height linked and set to 2600%, and Resample checked and set to "Nearerst Neighbor":

Then save a new copy (so you still have your original, if needed).