@Andrea Giuliani
saving is an option for the host only, if you are a client connecting to a server, you will need to configure the server to allow saves. other than serializing the mission data, i'm not doing anything special with the save feature so i'm not sure why it wouldn't work. restoring a save with different addon or game versions can be a problem but you should be able to at least try. do you get an error?

I have tried many of his Dynamic Recon Ops ACE scenarios but in none of them I can save the mission..

@gradje
in DRO's mission menu, if you are using ACE medical, ensure that "revive" is disabled and if you are using ACE advanced fatigue, ensure that "stamina" is enabled.

you can also reset the mission options to default from the button on the information tab on the DRO mission menu if you are the mission planner (the 1st player to join).

Squad wont move when starting up the game.

Yes! This is sick, thank you so much! Ace arsenal is better tbh-