I have no idea how to make a nice collider. All I can use is the Box, Sphere or Capsule. 
How should one approach this problem? I have just started using UE4 and this is what I’m struggling with now. I also don’t have any experience with 3D modelling, so yeah, but there is so much to learn! 
Forget to show an object? There are other options other than box/sphere/capsule in the collision drop down menu
Your model is Skeletal Mesh or Static Mesh ?
Working with collisions in UE is a little tricky. You have many options in setting up collision but we need to know more about your model. I couldn’t see any picture in your post!