Can I run Instagram myself without losing sales?

Yes, if you keep three slots a week and answer during service with the same rule. Sales slip when the story goes out after midnight and the midday message waits until close. Block on the diary the time to post and the time to clear messages, inside opening hours. The owner does it “after close”, and close is already too late for that night’s table. Your own week has three pieces and two written reply shifts, even if nobody else posts.