Very thankful for your comment. This is more of a playtest version where sadly there is still many bugs, including the things you mentioned.
1.Archers are needed for defense, towers can be populated by archers. 2.The saplings growth is by building ritual areas from the build menu. 3.Sending the merchant to expedition makes him return with gold to give to the player after a day.
You're playing a much older version and we haven't updated since we didnt feel the game is ready. Since then we have completely reworked the tutorial so it has more clarity. We have also been aware of said bugs and working on fixing them, hoping to upload a more up-to-date and less-buggy version soon. You taking your time to write a long comment is very precious to me, and i thank you again, hope you'll like the updated version better soon!