How to organize the translation of an entire subnet of IP addresses of the corporate network to your own local network?

Question

Computer networks

Corporate network: 172.16.209.192/26 with gateway 172.16.209.210. With its own characteristics:
1) It does not have the Internet.
2) There are applications running in this corporate network.
3) Asterisk IP telephony with E1 channel.
Now there is a PPPoE gateway (Mikrotik) with Internet and white IP.
Local network: 192.168.1.192/26 with gateway 192.168.1.210 - this can be changed.
It is necessary to provide Internet access to all machines on the subnet in any way possible without disrupting the operation of corporate applications and IP telephony.
I made a small plan:

PS Many-to-Many IP address translation would probably be a good solution...

Answer 1

netmap is just Many-to-Many
But not sure if you need it. You can do with the usual src-nat

Answer 2

Use src-nat Luke

Answer 3

172.16.209.210 what kind of device is this?