Need help with formulas

Here is the circuit

**broken link removed**

What formulas should I use to get values of Ua, Ub, Uc and Ud
How can I know which way I need to draw arrows ?

You will need Ohm's Law to calculate the voltages, and all the red arrows show current flowing toward the bottom of the drawing. Ohm's Law says: E=IR

This looks like homework. Is any current being drawn off the various voltage divider taps?

It is very unusual to ask for voltages "above ground." Most voltage dividers reference a voltage to the 0v rail.
The voltage on each "tap" will depend on the current being drawn by the ALL the outputs at any given instant. You cannot determine anything without knowing the currents.