How to connect 3 offices correctly?

Question

Windows

Hello! Please tell me how best to combine 3 offices, namely:
Office No. 1 has an external IP address 11.11.11.11. local network 10.10.1.0/24 In
office No. 1 there will be located: ​ ​ ​ ​ ​ ​ ​ ∙ system administrator workstation;​ ​ ∙Software that displays cameras from DVRs (receives RTSP stream on port 80); ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ∙ Mail server ;​ ​ ∙Web server 1C .
Office No. 2 (there is an external IP address 12.12.12.12. Local network 10.10.2.0/24) workstations of user2 employee and MFP. Scanning from an MFP must be configured to a shared folder (public\scan) located in office #1. The user2 employee must have read access to the public folder and write permissions to the public\user2, public\scan folders, access to the 1C web server, access to [email protected] mail. DVR with 16 cameras (10.10.2.100:80)
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Office No. 3 (there is an external IP address 13.13.13.13. Local network 10.10.3.0/24) workstations of user3 employee and MFP. Scanning from an MFP must be configured to a shared folder (public\scan) located in office #1. The user3 employee must have read access to the public folder and write permissions to the public\user3, public\scan folders, access to the 1C web server, and access to [email protected] mail. DVR with 16 cameras (10.10.3.100:80).
​At the same time, it is necessary to select network equipment and describe the network map and network packet routing, and how, in case of problems, will the system administrator connect to user2, user3 workstations?

Answer 1

https://habr.com/en/post/134892/ Right from the very beginning.