How to transfer traffic between networks?

Question

Computer networks

There is Mikrotik. It has a PPTP server and an IPSec tunnel to another city (also Mikrotik).
There is a subnet 192.168.100.0/24 , which is intended for PPTP clients (VPNs).
There is an office subnet 192.168.5.0/24 . And there is an office subnet in another city 10.10.5.0/24 .
And now the questions..
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When I ping from the 192.168.100.0/24 subnet to computers that are on the 192.168.5.0/24 subnet , everything works, because everything is standard.
But when I ping from subnet 192.168.100.0/24 to computers in the subnet of another city 10.10.5.0/24 , the ping does not reach.
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In other words, it is necessary that data packets can freely pass according to the scheme:
(192.168.100.0/24) <———> (192.168.5.0/24) <———> (10.10.5.0/24)
Packets from the 192.168 subnet. 5.0/24 to the subnet 10.10.5.0/24 and back run without problems, because the tunnel is configured.

Answer 1

return routes? - no, haven't heard
source nat? - no, have not heard
to study how routing works? - why, on the toaster now everyone rushes to help and they will do everything for me

Answer 2

Here is an easy decoding of what you were told above =)
Your branch 10.10.5.0/24 obviously does not know about the existence of 192.168.100.0/24, you need to tell it about it. Or pretend to be 192.168.5.0/24 when transferring from 192.168.100.0/24 to 10.10.5.0/24.