Average DNS response time worsened

iPhone 12 Pro Max (16.4.1) / iPad Pro (16.4.1)
　The events described below occurred with 16.4.x, rather than with the earlier version 16.3.x, etc,
　　The events described below did not occur with 16.4.x, but rather with earlier versions, such as 16.3.x.
AdGuard Pro: AdGuard For iOS 4.4.5 (990)
Safari blocking:
　　a) AdGuard Base Filter
　　b) AdGuard Mobile Ad Filter
　　c) AdGuard Japanese filter
DNS Filters (DNS servers and filter availability):
　　a) System default (filter: AdGuard DNS filter)
　　b) AdGuard DNS (no filter)
　　c) Cloudflare DNS (filter: AdGuard DNS filter)

1) Deterioration of average response time
For the past 2 to 3 months, the average response time of Adguard Pro has been slow, more than 1.0s.
The response time has been even worse, especially in the last 2 to 3 days, and we have never seen such figures as 40s to 54s.
The above may be the cause of the slowdown in web site display.
I remember that it used to be 7~8ms at the earliest and 20~30ms at the latest.
　Can it be speeded up by reviewing some settings or usage?
　
2) Worsening of filter update time
Even if you try to update the filter under Wi-Fi connection, it takes more than 1 minute to update the filter.
　(It used to take at least 10 seconds...). (I think it used to be 10+ seconds at most...)
Is it possible to shorten the filter update time?
　Does it depend on the hardware specs?