Need to configure 2 networks between Microtik as l2tpclient - softetherVPN?

Question

VPN

There are 2 grids, conditionally office and home. The office does not have a normal Internet, where the Internet distributes a USB modem plugged into Microtik, hence all the difficulties with a gray IP.
There is a home normal Internet, with a white dynamic ip with DDNS, too Mikrotik.
Accordingly, in both networks there are 24\7 servers on linux with SoftetherVPN, everything else in the figure was painted as best I could.

What is done, I tried to connect directly through VPN Azure Relay Service, the speed is very low and unstable, but it works.
I decided to connect network 1 as a client of VPN server 2, this is actually done, there is a connection, it remains to correctly register the routes in Mikrotik, as I understand it, I am not at all strong in this, and in view of the fact that, to the office (NETWORK 1) there is only remote access (via VPN Azure Relay Service) and there is a non-zero probability of screwing everything up with crooked handles, after which you will need to go to another city and manually reset the Mikrotik settings, which in the current situation you don’t want to do at all.



l2tp client connection