How is the price of the electricity I consume calculated?

The price depends on the time of day you consume it. With dynamic pricing, the price changes every hour, depending on the wholesale market.

Here is the formula:

Hourly price (€/kWh) = (EPEX Day-Ahead hourly price / kWh + €0.019*) × (1 + VAT)

In a nutshell:

the EPEX Day-Ahead price is the wholesale market price for each hour;
Frank Energie adds an amount in EUR/kWh to cover supply costs  
VAT is then applied to the total, at a rate of 20%.