I've seen this question but unfortunately it doesn't contain an answer to my question.
The question is: how can I calculate actual hashrate of the whole network? As far as I understand, it depends on difficulty in some way but I can not understand that dependency.
The hash rate can only be estimated from the difficulty, which is itself adjusted up and down based on how fast blocks are found compared to the 120 second target. This estimation is the difficulty (currently 7462457559) divided by the target (currently 120 seconds), so currently about 62 MH/s.