Let's find the inflection points, we'll need to solve the equation for this
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
the second derivative$$\frac{\left(\left(\cosh{\left(x \right)} - 1\right) \cosh{\left(x \right)} + \sinh^{2}{\left(x \right)}\right) \left(\frac{\cosh{\left(x \right)}}{\sinh^{2}{\left(x \right)}} + \frac{1}{\cosh{\left(x \right)} - 1}\right) + \frac{\left(\left(\cosh{\left(x \right)} - 1\right) \cosh{\left(x \right)} + \sinh^{2}{\left(x \right)}\right) \cosh{\left(x \right)}}{\sinh^{2}{\left(x \right)}} + \frac{\left(\cosh{\left(x \right)} - 1\right) \cosh{\left(x \right)} + \sinh^{2}{\left(x \right)}}{\cosh{\left(x \right)} - 1} - 4 \cosh{\left(x \right)} + 1}{\left(\cosh{\left(x \right)} - 1\right)^{2} \sinh{\left(x \right)}} = 0$$
Solve this equationSolutions are not found,
maybe, the function has no inflections