how to delete default rests in whole bars

Measure properties - shorten the value of the actual length.
But be careful: it is shortened from the right-hand side, regardless of whether there are notes or rests.
This is fine for the last measure, but not for the first. By the way: you can also set up the shorter first measure at the beginning, otherwise copy the notes, shorten the measure and insert them again...

You can only delete rests in voices 2, 3 or 4. Better is to make them invisible by selecting them and using keyboard shortcut V. They will show as grey on screen but will not print. You can turn off the display of "invisible" elements in the View menu or (assuming you are using version 4) you can get a true WYSIWYG in the Publish tab where non-printing elements are not shown at all.