How to fix characters to display animations as intended by animation author?

Hi, in Unity, i bought this cool set of combat animations, they look perfect on the doll that came with the animations, but it doesnt look good at all on my characters, even though they are both humanoid and mecanim ready.
it looks bad, and transition from motion to another looks glitchy specially on transition from attack to idle.

question is, can i solve this within Unity or i have to use other engines like Blendr?

i reached riggers in Fiverr and they all seemed having trouble solving this, so another question, is this even solvable?

to demonstrate my problem, i feel i have to share with you some files, these files are partial, so it doesnt have materials, and animations are not complete, only four motions are added out of 40.
https://drive.google.com/file/d/11EAOrLgEV0OSJzDenJ4YkvImkhPcgboW/view?usp=sharing

ive been having this issue for almost two months, and i feel bumped, i had so much plans for these animations on my characters.