How to combine the Internet from different providers through mikrotik?

Question

Mikrotik

There are 2 different providers.
1. 20 mb/s
2. 5 mb/s + 100 mb/s to the internal network (torrents are primarily interested)
You need to combine the Internet from these providers, but port forwarding to mail, telephony, etc. is already configured through provider 1, and this mikrotik is an l2tp server for other remote offices (and all this disgrace through the ip of the 1st provider).
What is the best way to organize this?

Answer 1

lanmarket.ua/stats/mikrotik-routeros-dva-provajder...
well,
habrahabr.ru/post/231565