Why is the Internet slow and sites with https do not open?

Question

Mikrotik

Mikrotik rb951ui 2hnd was inherited, to which 2 providers are connected: from one provider they sit on the Internet, and from the other a connection is made with cameras in the garage and in the country.
After buying Xiaomi Mi WiFi 5g, I disabled wifi from Mikrotik.
After my manipulations, sites with https broke down and the Internet began to work slowly.
I have no idea how to restore the normal operation of the router.
Config (made via /export hide-sensitive)
Google doc

Answer 1

I have no idea how to restore the normal operation of the router.

Why then climbed something to change? Find someone who will come (with their feet), look and fix it. It will most likely cost money.
But for the future science:
Works - do not touch!
You touch - be sure that you can at least return it as it was!

Answer 2

When there is a problem with TLS/SSL, it is most likely worth the DF bit, and since you have pppoe, you need to edit the MSS for TCP,SYN packets.