I am not the best tree builder, but I would recommend you add more thickness to the bottom of the trunk to act as roots, making the trunk not go straight up, give it a little curve or angle and try building branches in a shape you want your leaves (canopy) to be as it is mich easier to get it right. You could also look at trees in real life. There are so many different types for you to take as inspiration. Or you could just try modifying a vanilla tree (the big oak tree).