Before you start the calibration check if you have the grid calibration enabled in the smoothieware config file:
My config has this:

#Example for the delta grid leveling strategy
leveling-strategy.delta-grid.enable true # Enable grid leveling
leveling-strategy.delta-grid.radius 140 # Grid radius in millimeters
leveling-strategy.delta-grid.size 29 # Grid size, must be an odd number


The bigger the grid size, the more points it will test and the longer will take.

Heat the printbed to the temperature you normally print with.

Do the grid calibration:

; home
G28

;bltouch alarm release
M280 PS10.6

; probe pin down
M280 S3

; set bed temp to 80C
M190 S80

; do delta calibration
G32

; save trim to sdcard
M500

; probe the grid and enable grid compensation
G31

; save the grid to sd card
M374

;To set the zero for the print head
;Make sure there is no left over material on the nozzle ( maybe heat and wipe it )
;go home
G28

;go close to Z=0
G0 Z1

; put a sheet of thin paper under the nozzle
; Then move the head ( using the printer controls ) until it presses on the paper sheet, until ; you feel the friction when you pull on the paper. This is the Z=0 point
; Use this point as the homing offest
M306 Z0

;save to SD card
M500

But even after all this it seems the prints are still not all right, so another option is to do some manual calibration of the hotbed using some springs.