Problems after updating the router firmware

Good day, friends.
There were problems with the router + tv. I decided to update the firmware. Router TPLink tl-wr841N / I downloaded the latest firmware for my model from the site's office, updated according to the instructions and everything seems to work, BUT
now ping, packet loss and other delights of poor communication are off the charts on all PCs . Also, now the download speed from the Internet is low, although the speed test shows 100 megabits. Moreover, if you connect the Internet to the PC directly, bypassing the router, everything is fine.
I tried to roll the old patch, again a new one, reset the settings - nothing helps.

those support of the manufacturer of the router, as usual, feeds shit, the provider says that the problem is not on their part.
All hope is on you, comrades