The following could be the reasons if your toilet isn’t flushing its contents all the way:
-The poor toilet drain pipe design.
-A clog in the toilet, flange or drain.
-The water level in your toilet tank is set too low.
-Blocked inlet holes.
-Problems with your flapper.
I think it's better to call a plumbing service to get this fixed. It's not just gross, but it's wasteful and annoying when your toilet doesn’t fully empty its contents when you flush. So, rather than 'DIY-ing' get the help of a professional as soon as possible.
The following could be the reasons, if your toilet isn’t flushing all the way:
-The poor toilet drain pipe design.
-A clog in the toilet, flange or drain.
-The water level in your toilet tank is set too low.
-Blocked inlet holes.
-Problems with your flapper.
You can also refer this blog
Easy Steps To Fix A Clogged Toilet Without A Plunger | Brothers Plumbing Company for easy steps to fix a clogged toilet without a plunger.
I think it's better to call a plumbing service to get this fixed. It's not just gross, but it's wasteful and annoying when your toilet doesn’t fully empty its contents when you flush. So, rather than 'DIY-ing' get the help of a professional as soon as possible.