difficult always increase possible they to decreasee or less than before ?
I'm not sure I understand the question, but I think you're asking if it's possible for difficulty to decrease?
if so, the answer is yes, it's possible, and in time it's likely to happen, or at least level off. We're at the first major pause in a major technological arms race. It has slowed down considerably.
Technically speaking (well, referencing anyway), the network adjusts difficulty to maintain an average of ten minutes between blocks. If the hashpower goes down somewhat during the 2016 blocks between adjustments, then it will drop to make the times work out. I don't believe this has ever happened, definitely not in the two + years I've been involved in BTC. But it is technically possible, and as the diff rises, there will probably come a point where a bunch of older mining equipment is taken off line due to being too expensive to operate. During that period, it will probably drop a small amount or remain level. We've already seen a couple of difficulty adjustments under ten percent rise.
But there is also ongoing technological development, and many of us working to bring bitcoin and other cryptos to the mainstream, so don't expect it to decrease any time soon. I have used 15% per period as my middle case calculation for some time. It's never been accurate, but it has been close to the mean for some time.
thanks agree with this what we se not always true . different like in predict right .