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
Industrial mining farm are stil very profitable. Here is a nice graph user Puppet posted in several threads:
Doesn't matter what the J/GH is if you can never recover the capital cost of miners even with free electricity, which is where bitcoin mining stands right now.
You couldnt be more wrong. Here is a chart for you:

It shows the network speed where miners would break even after 2 years using the listed assumed variables. Even in the current climate and with current efficiency, we are no were near where (industrial) mining would not be profitable. And the effect of power efficiency is quite dramatic if you consider reasonable electricity cost price ranges (~0.06 / KWh)