Stuck - Alien Time Zone

[CuteLittleGuest]

Hi, everyone. I have problem moving on with the game. This is what I did so far

Spoiler

created crystal, gave crystal to robot-worker, got digging tool - sorry, I don't know the word for it -, went to the 1600s and opened a hole on the wall for the old man to get fresh air. So, I was expecting that I could get the old man to give me the key.

[close]

I talk to hom but nothing happens. I have no idea what to do next. Please, help me!

[Tessera]

Just a hint:
Travel to the future