It literally shows what you're missing in your screenshot. oO The strategy battle system can be unlocked when you repaired the barracks where you found Mira, and go back there to meet the vanguard squad leader Jessy. She has the quest which unlocks the system.
No idea what problem you have with the trade. Did you perhaps order Theremis in your throne room to close the borders to Amagal/Begus?
this i am wanna change begus trade