Morello cherry tree

Hi, My morello cherry is only showing signs of life on the end of the branches, is there anything I can do to make it fuller again, I’ve attached a photo from last year, many thanks in advance

 

Hi, is there anyone out there that can help me.My morello cherry is only showing signs of life on the end of the branches, is there anything I can do to make it fuller again. It’s a memorial tree so I really don’t want to lose it. I’ve attached a photo incase it might help. Many thanks

 

See :
www.rhs.org.uk/fruit/cherries/grow-your-own
paragraph 5 refers to pruning.