First, I would fill the cracks with wood from the top, even slightly bending the crack so that the wood would go as deep as possible, then dry wipe the white surfaces where I expect compression, glue the left white side surface intended for compression everywhere with a 4 cm wide colorless tape, place a wider vertical board under it and place it on the glued colorless tape and on the gap, and squeezed it with two carpenter`s clamps, placed on the entire door frame together with the board, but one should be in front of the transverse gap and the other one lower, and waited at least 12 hours, and painting on the next day , after removing the colorless tape. After squeezing, wipe the front surface of any wood that comes out of the crack... The wood is white, sometimes the joint will be so white that you don`t need to paint it...