Add this code to the Divi-->Theme Options --> Custom CSS Section

/* Change projects protfolio columns from 4-3 start */ 
.et_pb_column_4_4 .et_pb_portfolio_grid .project {
 clear: none !important;
 margin: 0 60px 42px 0 !important;
 width: 27% !important;
}
/* Change projects protfolio columns from 4-3 end */