it seems an average of 5% increase, and i cant understand, how difficulty is still increasing with these btc prices.
Because people are still adding hash to the network. Those with cheap electricity and cheap hardware still turn a profit even at the decreased price of BTC.
In order for miners to continue to be profitable on an operating basis they will need to have ever additional cheap electricity as difficulty increases, and this is exaggerated as the price of bitcoin goes down. Miners will also be hesistant to add additional capacity to their farms as the price of bitcoin goes down as the lower the price of bitcoin is the less of a chance they will be able to ROI on their additional investment