Change note lenght + staccato

If they are all followed by a rest, 8th or longer: select the range, right-click one of the notes, Select/More.../Same duration,In selection/OK, 5, then double-click staccato

Edit: Hmm, so far for the theory, unfortunately this doesn't work.

Unfortunately there is no option to change the rhythm in a large section of the score in bulk. Unfortunately the only thing you can do is select the first one press 5, right arrow, 5, right, 5... until the notes are fixed. The longer notes will overwrite the rests. Once the notes are correct you can select the entire range is press shift+s to apply staccato to all of the notes as once.