I'm searching for software which can solve problems regarding engineering mechanics, it will be perfect if it can solve statics, kinematics, dynamics and material mechanics.
Have you tried Matlab? It has add-ons for most fields of engineering. It was designed to be a working environment for engineers. It is not cheap. The basic package is but add-ons can be expensive. There is a free option called Octave. An open source version of Matlab. I don't know the status of add-ons for Octave. Matlab is developed by Mathworks and has a large user community. If you need an open source solution I'd look into what add-on packages are available with Octave.
Considering you tagged this question "open-source" you might consider Python scripting with NumPy, SciPy, and Matplotlib.
Professional/paid solutions include Mathematica and Maple.