The question is absurd.
'Truths' and 'untruths' only exist in 'thought/ego'.
It is a matter of Perspective whether you find something truthful, or not.
What you find to be 'truth', another will see a lie!
"For every Perspective, there is an equal and opposite Perspective!" - First Law of Soul Dynamics
So for every 'truth' there is a 'lie'.
As far as how many, just count the Perspectives (almost infinite!)!
How many 'truths'?
How many 'beliefs'?
Everyone infected with 'beliefs' imagine their 'beliefs' to be 'truth/Truth'!
Re 'infinite';
'Infinite' is a poor term as no one has ever witnessed such a thing.
Perhaps 'near enough' to be handily called 'infinite'.
How many photons have existed/exist in the Universe?
Now many neutrinos in the Milky Way Galaxy?
For all intents and purposes, 'almost infinite' is the more precise term.
Not anything is perceived that does not exist, and vice versa.
No one perceives the 'infinite'.
It is a useless a term as 'nothing'!
As far as capital 'T' Truth is concerned, there is only one ALL INCLUSIVE Truth/Reality!
One must start removing vast swaths of Reality (ignorance) to imagine lies.