How to change several Note's duration without adding a rest

[Jerome_F]

Hi.
I have a line of notes played with Crotchet.
Now I want to change it to be played faster Quaver.

If I already have a few notes, each one is 1/4 duration (Crotchet).
Do - Re - Mi - Fa ...
And I want to change the notes duration to be 1/8 (Quaver).
As far as I know - I select all the notes in the bars I want to edit,
then I press the Quaver icon (number 3 on the keypad).
What actually happens in Sibelius is that all notes do changed to quaver,
but instead of kipping the line, it adds a rest between each note,
so if I edit two bars - the total length is still 2 bars instead of 1 bar but faster.
(do - rest- re - rest - me - rest - fa - rest ...)
1) How can I do the modification without adding the rest in between notes?
2) another question - with a connection to the last question but also stand by itself -
If it already happened - How can I delete a rest but without leaving empty space? usually when I delete a rest - all the notes that come afterwards are staying in their position. (so the rest doesn't displayed but actually is there).
Is it posible to delete a rest and make all other notes come one step backward?

Thanks a lot.
Hope you understand my long questions...
see picture attached