[Help] Model is bending weird

[HumanDude]

For one of my models i'm trying to get a normal look to it with the way the bones bend. For some reason the legs don't bend like they do on some normal default avatars. Instead of the legs and feet sticking in front of the hips it goes directly under and the knees are low. The chest also goes more straight up then leaning slightly forward. This causes the head sometimes to stick out in a weird way that looks unnatural. Here i will show you two pictures, the red is bad, the green is how i want it to be.

https://imgur.com/a/pRGj5KZ

https://imgur.com/a/CdGfjKB

I've tried multiple things to fix this like the parenting warning in unity when uploading a avatars, i tried to use cats with different settings on the fix the model, i also tried to make the bones go in the correct direction in blender (leg bones point down, upper bones point forward through the body). I'm not sure what i'm doing wrong but i can't find much on this. If anyone knows what causing this and a solution i would very much appreciate it.

[Makoto (真)]

I'm not sure how to do it, but it might be a weight painting issue. See if you can find a tutorial for weight painting in Blender. Again, not 100% if that's going to fix your problem, but it might.

[SHOKK♥]

It's not a weight paint issue.

It's just how the IK works with the bones, it's hard to judge what to fix, sometimes even the length of bones can make things different.
It's just a issue that's inevitable.