After some bad decisions, my village only has one person left. I know that once he dies I will get new villagers but I was wondering; will all of my solved puzzles, mango trees, lift, bath etc. be gone? Will I have start all over again?

Unless you get an event, yes you will have to start all over again. But don't give up just yet! Read the Story of the Hard Tribe by IBteri. She had something very similiar happen to her, but it has a happy ending.

Don't stop you're tribe yet. An event might come. It has happened to ne before.

If not, then yes, you will have to start over.

i just wanted to add, i hope your luck changes

thanks everyone you are all very kind!

I let my first game run overnight and in the morning I came in to find only one little girl left. I tried to hang in there and wait for her to get old enough for an event, but I finally just started over because I think she was only 9 or 10. But I did get an event in another game, so I hope you will as well. Keep us posted!